Idle Tuning How-To & Guide (w/pictures)

IDLE TUNING

Foreword by Rinkrat456: This article is literally copied and pasted from Krambo's Silverado SS page. He is an HPTuners member on this site. I take ABSOLUTELY ZERO CREDIT for the length of material you're about to read, however I have made a few comments in-text that you can see which I will highlight in green. The pictures within this how-to are my contribution to aid in explaining what Krambo is trying to tell you. I have used this guide before with positive results and nothing jumps out at me as Krambo trying to pass on poor advice. I HIGHLY recommend reading through this entire guide before attempting to make changes to your engine. If any of the links stop working, PLEASE PM ME so I can fix them.

Enjoy! :chug:

The following is a collection of idle tuning notes, tips ‘n tricks and How-2’s for idle tuning a big cam (or any cam for that matter) that I used when dialing in my 248/254, .615"/.622", 112 LSA using HP Tuners. If you choose to follow any of these How-2’s, please do so at your own risk and do one change at a time…in other words, I am not responsible if you blow it up or damage your engine. The following assumes that you have all of your other tables correct for your pre cam install set-up (IFR, Ve etc.). He means this too...don't skip straight to fine tuning your idle if you're unsure of your injector data or you know ahead of time that your VE table is garbage. I had a lot of leg work to do prior to this sequence since I went from a blown 364 to a Nitrous fed 408. O.K. If you are not familiar with the tables in HPT, this may be very confusing. To those that have the software and can follow, PLEASE ADD YOUR EXPERIENCES, so this thread can be utilized for all the do-it-yourself tuners. <<<I took his advice and now this is what you're reading.

Alright, you have your new cam installed, degreed and ready to fire. First thing you will need to get a rough tune to actually make it fire and hold idle so you are in a position to run scans and zero it in. As a GERNERAL guideline, you can follow this suggestion:

Cams with negative overlap up to zero, set idle to 850-900 all cells across the board, add 1 g/sec to idle airflow across the board both in P/N and in gear (HPT > Engine > Idle > Idle Airflow > Base Running Airflow), add 2º of idle timing 1200 rpm and under and 0.08 – 0.28 g/cyl inclusive (HPT > Engine > Spark Control > Spark Advance > Idle Spark Advance (in Park).

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Cams with over 0º overlap up to 15º, idle 900-950 all cells across the board, add 2 g/sec to idle airflow across the board both in P/N and in gear (HPT > Engine > Idle > Idle Airflow > Base Running Airflow), add 4º of idle timing 1200 rpm and under and 0.08 – 0.28 g/cyl inclusive (HPT > Engine > Spark Control > Spark Advance > Idle Spark Advance (in Park).

Cams over 15º overlap, idle 950-1100 all cells across the board, add 3-4 g/sec to idle airflow across the board both in P/N and in gear (HPT > Engine > Idle > Idle Airflow > Base Running Airflow), add 6º of idle timing 1200 rpm and under and 0.08 – 0.28 g/cyl inclusive (HPT > Engine > Spark Control > Spark Advance > Idle Spark Advance (in Park).

You can go to this link --> Overlap Calculator to determine your cam overlap. Have your cam card handy and follow the inputs in the calculator. My cam has a very healthy 27* of positive overlap which is on the very high end of any cam you will typically find on a street driven truck.

Confused already?...are your units as you want them to be? Are you stuck in lb/min or g/sec? Right click on the cells, scroll down to "UNITS" and select the way you want your data presented to you.
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Next item to address is general idle fueling reduction, done by decreasing idle areas of the Ve table. Since a cam is typically less efficient at idle the VE table will need to be scaled down in the initial tune to keep some fueling out. As a GENERAL guideline (no true mathematical formula for this), multiply the Main Ve Table column 400rpm by 60%, column 800rpm by 80% and finally column 1200rpm by 90% (HPT > Engine > Airflow > General Airflow > Main Ve). Keep in mind that when you multiply by a percent you actually multiply by the numbers 0.6, 0.8 and 0.9 respectively. Do NOT multiply by 60, 80 and 90! Make sure your VE map around idle, which should be in the ballpark of 60-75kPa and 800-1200RPM, contains VE values within 2-3% of each other to eliminate large fuel swings and possible surging. Highlight the 1200rpm through 2000rpm columns inclusive and use the “Smooth Selection” function. This will give a nice curve and should avoid surging due to fueling. In my opinion, take this part of the guide as a wake-up call to expect that less fuel will be needed with a big cam down low. If cutting down to 60%, 80% and 90% prevents the engine from starting because it doesn't have enough fuel now, add fuel back. On smaller cams you don't have to cut as much fuel as big cams. Small cams may be able to simply start right up using the factory VE cells around idle. Take note if your operating system uses a primary and a secondary VE table in case you find yourself in Speed Density mode, which then your secondary VE table is referenced. Whatever changes you make to the primary VE table will have to be manipulated in the secondary VE as well.

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Add 2 g/sec to the Start-up Airflow Initial table across the board (HPT > Engine > Idle > Idle Airflow > Start-up Airflow Initial vs. ECT). <<You'll want to revisit this table once you have your base running airflow dialed in fairly well to avoid start-up flairs. Look at an LS6's table for reference.

Add 50 camshaft rotations to the Idle Start-up Airflow Delay vs. ECT (HPT > Engine > Idle > Idle Airflow > Start-up Airflow Delay).

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Make sure that your Idle Spark Advance table (both “In Drive” and “In Park”) match your High and Low Octane Table for all columns up to 1200rpm (HPT > Engine > Spark Control > Spark Advance > Idle Spark Advance (in Park, in Gear), Hi and Lo Octane). Blend the timing numbers into the 1600rpm+ columns so there are no huge numerical transitions. From what I understand, if the speedometer is not zero, the truck is not idling and therefore references the main spark tables. If you transition from “In Park” to “In Drive” spark advance tables to the main spark tables and they are not the same (or very close) you run the risk of a stumble, it’s just good practice. You'll have to come back to these tables once you find exactly where your cam likes to idle for spark...there's a part in this guide explaining how to find the "strongest" map value using the spark advance in the bi-directional controls of the VCM scanner. Once you figure that value out you can come back to these 3 or 4 tables. See picture

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I'll also add that I believe most of us can benefit from commanding stoich after the engine comes up in temperature and continues to reach operating temp. To do this during the idle tuning process, go to Engine > Fuel Control > OL&CL >Open Loop EQ Ratio and set columns 140-230*F to = 1 which will command the PCM to set fueling to ~14.7. Smooth the transitions by selecting the neighboring columns if you wish. You'll have to force the PCM to stay in open loop as well, which means setting the Closed Loop Enable ECT vs IAT table to Max value (284*F)
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With all of the changes done above, the truck should fire and hold idle. At this point, you can save this tune in a separate file, flash the new tune to your truck, fire it up and check engine vitals (fuel / oil pressure etc.) and get a heat cycle into your new valve springs (assuming you swapped them) OR you can dive strait into logging for the Desired Base Running Airflow numbers based on your specific cam and engine set-up.

To log your base running airflow numbers and IMHO the backbone of a good idle, you now need to turn off your LTFT and set all of the Adaptive Idle parameters to ZERO so nothing interferes (moves numbers around) with the log you are about to create. To do this go to HPT > Engine > Fuel Control > OL&CL > Long Term Fuel Trim Enable, and make both the Min. and Max. ECT settings equal to 284*F <<or on some vehicles just use the drop down menu to disable. Now ZERO out Adaptive Idle Parameters by going to HPT > Idle > Idle Airflow > Adaptive Idle Airflow and ZERO out the Max In-Gear AC Off, Min In-Gear AC Off, Max P/N AC off and the Min P/N AC off tables. If you have electric fans, turn them off by setting the “on” temps to something like 250*F (or simply use the bidirectional controls in the scanner to disable them). Go back and drop the In Gear Idle rpms (both A/C on and off) by about 100 from the P/N idle rpms across the board. Save this tune file with a file name you can remember (i.e. Idle Airflow Tuning) and flash the PCM with these new changes.
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Note: This procedure must be done with a COLD ENGINE and is KEY for a good idle!

Download and Open the idle-airflow.cfg that is attached at the end of this post. Use the VCM scanner to open the .cfg file.

NOTE! Those who set their idle at 850-1000, don't leave it like that. The purpose of setting the idle high for your first few times starting a brand new build is to simply get it stable enough to monitor with the scanner. I do not recommend keeping it like this and I don't think Krambo is trying to say that either. You will want to adjust your target idle speed before attempting to dial in your base running airflow. Here are a few examples of three LS1's I've done recently to show some examples.

Here's the 5.7L in my Sonoma. It's a truck-oriented off road engine built into a 5.7L from a 5.3L using a 206/212 112lsa cam.
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Here's an LS1 example with a 22x/23x 115lsa cam in a C5 Vette
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Here's another LS1 example with a 23x/23x 112lsa cam in a custom Mazda
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Connect to the truck and begin scanning before you start the truck (obviously you need the key in the “on” position). Reset the LTFT using the VCM Controls (VCM Scanner > VCM Controls > Fuel & Spark > Reset Fuel Trims). Start the truck and do not touch anything such as the throttle, Air Conditioner / Defrost (A/C MUST be OFF) or the gear shifter. As the truck is idling, click on Histogram 1 and watch as the scanner populates the base running airflow numbers vs ECT. Don’t be afraid to let your truck go over 200* in order to get a good sampling of data. I try to do this on a cold morning and I use the VCM scanner controls to disable the fan(s) until I think the engine is warm enough (usually 235*F I call it quits if the vehicle even can get this hot with the fans off).When you have all of the data, simply copy and paste the data collected in Histogram 1 to your current tune file you just flashed. The data will be pasted into the Base Running Airflow table (HPT > Engine > Idle > Idle Airflow > Base Running Airflow) for both P/N and In-Gear. BE SURE TO PASTE THE NUMBERS IN THE CORRECT CORESPONDING CELLS! Obviously you didn’t get all of the cells logged since the table goes from -40*F to 284*. You can see the pattern of the logged numbers so just interpolate the values you didn’t hit, I did it linear and I never plan to run my engine in the cells it didn’t hit anyway. Again, save your new tune and reflash into the truck and let the truck cool down for at least several hours (I let it cool down over night). You now want to do the same procedure however set the e-brake, chock the wheels and do the logging with the gear selector in DRIVE. Be safe here and stay in the driver’s seat during the entire procedure. Just as before, do not touch the throttle, change gears or run the A/C or Defrost. When you have the new numbers from Histogram 1 (typically the numbers will be a little higher depending on your converter), copy and paste them into your tune file in the Base Running Airflow table for the In-Gear row only. Again as mentioned before, be sure to copy and paste in the correct cells. Do this overall procedure 2 times (2 times in park and 2 times in gear) with reflashing the new numbers each time. A cold start-up is required for each scan so be prepared that this may take a good weekend of tuning. This procedure will get you real close to dialing in your Base Running Airflow table and you should notice a significant improvement on idle quality especially transitioning from Park to Drive after each set of new numbers entered into your tune.

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NOTE: If for some reason the units in the config don't look right where you're pasting the new data into the tune, check the units!

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Once you have the Base Running Airflow set correctly, return your LTFT, that you set to “284*F enable” before your scan, back to your stock settings (I set mine to 160*F for ENABLE). While you have your file open, set your Min temp for adaptive idle to an appropriate temperature (HPT > Engine > Idle > Idle RPM > Adaptive Idle RPM Min ECT). As a guideline, it should be *about* 30 degrees cooler than your engine normally runs. If it runs at 180 when warm then 150 is your target (this is typical for a 160* thermostat). Max temp -- leave it alone, I run mine at 220*.

As a guideline, your STIT & LTIT should be within +/- 0.75 to 1.0 g/sec after this tuning procedure. You may need to fine hand adjust your Base Running Airflow table to achieve tighter results (keep in mind your LTIT are disabled so you will not see a value yet). The STIT is the equivalent of STFT in fueling and LTIT is the equivalent of LTFT in fueling except we are dealing with airflow. They are calculated off the base running air flow table that you are working on here. It is an adjustment (+/-) to that base airflow table. The STIT & LTIT add together to offset the base running airflow to keep the engine idling properly. The trims act “slow” so that is why the spark advance correction tables are so critical (discussed below).

Put the MAX Adaptive Idle Airflow values you zero’d out previously back to stock (4.50g/sec) and put the Min values to -0.5 g/sec or less. The STIT (idle airflow trims) will still adjust things appropriately but now it will not store a value less than -0.5 g/sec. Setting the Min Values to -0.5g/sec is very beneficial for big cams as on a hot restart more airflow is necessary. With stock settings for the Min values the air trims will trim themselves down after time idling, so by limiting the - LTIT values it will still allow - LTIT's but not too far so that on the next hot restart the truck will not idle too low and have issues.

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SAVE ALL OF THIS GOODNESS YOU HAVE BEEN WORKING ON! I save it to a different file called “Working Tune” personally. Flash this new tune with all of the updates into your truck. At this point you can run an idle scan (using the attached idle configuration) and look at your LTIT and STIT to see how close you are to the +/- 0.75 to 1.0 g/sec. Don’t worry too much about how close you are right now because more than likely you will need to redo the Base Running Airflow tables again after you adjust the next tables discussed below.

By now, your new cammed truck should be idling pretty well (unless you have a cam like mine) so you can go into some of the finer points, one being the Idle Overspeed and Underspeed tables (HPT > Engine > Spark Control > Idle Adaptive Spark Control, Overspeed and Underspeed). (*Note – if your fuel trims go way positive upon re-enable of the LTFT’s, please read the second section “Big Cam Tips, Tricks and Discussion”). The PCM uses spark advance/retard and/or IAC/throttle blade movement to control idle. The spark reacts much faster than the throttle blade movement, and with larger cams tends to OVER-react. This tends to cause the idle to drop too low, or jump too high, which then causes the PCM to try to correct it back the other direction again using the Idle Overspeed and Underspeed spark correction tables. In your scan, look at the timing line in the chart view…does it bounce high and low or does it remain relatively stable (+/- 2*)? If it bounces around quite a bit, it may be a good idea to adjust these tables. Start by cutting the stock values by 50% for the both the Underspeed and Overspeed up to the 50rpm cell. Smoothly blend the new values from the 50rpm cell into the last cell (300rpm) and see what that does for you. It really helped my saw-toothed timing line and smoothed the roughness quite a bit, the stock tables are agressive.

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Update RPM error time (HPT > Engine > Idle > Idle RPM > Adaptive Idle RPM > Update RPM Err Time) can be set to ~0.4 so the STIT reacts a bit faster on mildly cammed trucks. “Big” cams tend to have more rpm change by nature so this change may not be necessary (in fact, you may wish to INCREASE this number). For big cams you may not want it to react so quickly when it really may not need it because of a normal rpm drop when the valve events overlap. You will need to experiment here as each application is different. I use 0.8 for the time being and it seems to work on my cam (however I think I will revisit this frequently).

Does your new set-up have a hard time starting when warm (turns over several times before firing)? You can add another 0.5-1.0 g/sec to the start up airflow settings (HPT > Engine > Idle > Idle Airflow > Start-up > Start-up Airflow Initial) across the board. Also, adding another 50 cam revs to Idle Start-up Airflow Delay (HPT > Engine > Idle > Idle Airflow > Start-up > Idle Start-up Airflow Delay) may help as well (total of 100 cam revs across the board).

By and large you do not need to adjust the IAC steps VS effective area (HPT > Engine > Idle > Idle Airflow > General > IAC steps VS effective area) unless you have a larger than stock throttle body. Also the ETC Area Scalar (HPT > Engine > Idle > Idle Airflow > General > ETC Area Scalar) falls into the same category. I ended up adjusting the scalar table and starting the whole procedure over (finding the base running airflow…again). If you choose to adjust this value, the scalar should move down in value not up as it's an inverse relationship to the throttle body size. For a 90MM LS2 TB, use 0.0190. Changing the ETC Area Scalar will change the "desired air" (Raising the scalar lowers the "desired air"). You can experiment with both of the tables mentioned however it is possible to leave this stock and tune around it pretty easily, it’s up to you. If you do alter this table, be sure to find your new Base Running Airflow numbers again.

Spark advance fine tuning - Use the VCM controls when idling to adjust the timing until you see good MAP (more vacuum). I turned off adaptive spark using the bi-directional controls with the scanner (Spark Idle) so I had a steady, flat timing line and could actually see if there was MAP changes. Do this by going to the VCM bi-directional controls and disable the Adaptive Spark Control (called “Spark Idle” under the fuel and spark tab) by actually clicking the “ON” button. Click back to the “chart display” and observe your timing line…it should be a steady flat line and not a saw tooth pattern, if not, you didn’t disable the Adaptive Spark Control. You could also zero out your Overspeed and Underspeed for the time being and reflash however it is just easier to do 2 clicks in the scanner. O.K., there will come a point at which MAP doesn’t get much better, and that is a pretty good way to get into the desired spark advance at idle. Listen to your engine for idle quality as well. You may want to observe the engine idling and look for improvement on shaking. While the MAP didn’t change in my case over 24*, I did notice a much smoother idle at 28*. If you get some idle surge, chances are you may have too much timing in there (if your base running airflows are tuned and your fueling is good). Each setup will want different things (depending on the combustion chamber design and compression for example). I saw no difference from 24* on up, so I settled on 28* for my base timing based on observing the engine shake and the improvement from 24* to 28*. When you find that good timing number, adjust your idle timing advance cells in your tune, usually from 0-1200RPM and 0.08 – 0.28 g/cyl (remember…do all the timing tables: Idles and Mains!), save and reflash the new changes to the PCM.

Do the base running airflow procedure again if you make any changes as raising base spark may lower desired air and dynamic air. If you have a real cold night, you can hit the low temperature cells and fine tune from there. If you do this procedure in the summer, expect to do it again when it gets cold so you can hit those colder cells. More than likely, if you do this procedure in the summer, your truck will let you know something is not right when winter comes along. Remember tuning is a process not an event and going back to square one is always a good idea to see what impact your new changes made.

Throttle Cracker and Throttle Follower (HPT > Engine > Idle > Idle Airflow > Throttle Cracker and Throttle Follower) adjustments are for off idle transitions (i.e. coming to a stop). As a guideline (since your standing idle is now fairly dialed in), zero out your cracker table from columns 400-1000rpm and through rows 0-32mph. Set the 1600rpm column from 0-12MPH to zero as well. Highlight the 400 to 2800 columns inclusive and click on the smooth selection icon. Again, smoothing is a good idea for proper transitions. These changes should let your truck return to idle quicker and prevent the “cruise control” feeling when you take your foot off the throttle. Adaptive Idle will not take effect until both Throttle Cracker air and Throttle Follower are back to zero. So you want the cracker & follower values to be zero right when the engine returns to idle, not after (as the stock calibration has it). The “Cruise Control” feeling is also a product of too much Base Running Airflow however since that table should now be dialed in, more than likely your Throttle Cracker Airflow table is to blame. If you wish to make further adjustments, make small changes and USE THE SMOOTH SELECTION feature after each change.
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Throttle Follower parameters do not need too much adjustment IMHO. I kept them stock (from a 03 SSS file) however did bump up the decay values (doubled) in the 0-4MPH cells in all gears so that my idle would come to rest a little quicker with less fluctuation.

Air conditioning fluctuations. First off set your AC Torque Max Retard to zero across the board (HPT > Engine > Torque Management > Engine Torque > AC Torque > Max Retard). If you have issues with a bad stutter when the AC engages, up your “Idle RPMs with the A/C on” (both in gear and in P/N) only by 50RPMs across the board. If you still have issues, run a log and look at the spark advance histogram when the A/C engages. Find what g/cyl is referenced at that moment and increase your spark tables in that area to improve stall resistance / stumble (don’t go crazy with the timing though a few degrees may be all that is needed). Another suggestion is to lower the A/C Torque TPS Max. (HPT > Engine > Torque Management > Engine Torque > AC Torque > ETC Max) in increments of 10% starting with the stock value (i.e. if stock setting is 10, go to 9 and try it, and so on) but do not go lower than 2.5%. I personally did not mess with this setting as I had no reason to. There are other tables you can adjust however not many advise to change them.

Misfires. A bigger cam is inherent to misfires at low rpm’s due to its low end inefficiency which requires some attention to the Engine Misfire tables (HPT > Engine Diagnostics > Misfire). I do not have a general guideline here other than increase all tables. The max value you can enter is 32767 so I would suggest starting with 20% of that number and increase as you trip a DTC for the P0300 (Random Cylinder Misfire code). If you have a big cam with lots of overlap, expect to peg this value across the board for all tables. If fact, I ended up deleting the P0300 code as it was a nuisance. Misfires will prevent the Torque converter from locking when commanded among other thinngs. Deleting this code prevents this in my case.

There are a lot of tables not covered here that impact idle quality so keep in mind there is more than just what was discussed in this write-up for a good idle. I would say, that using this procedure, 99% of you will be in good shape. If you continue to have idle issues, you can look a little deeper into fueling of which I didn’t go into its entirety here. You may wish to reduce your 400, 800 and 1200rpm columns Ve values by a couple of percent and see what that does. Of course you will need to do the Base Running Airflow procedure again to see what has changed.

Big Cam (lots of overlap) tips, tricks and discussion:

After I had my base airflow pretty well dialed in, fueling appropriate and timing where it should be and re-enabled my LTFT’s… it all went to hell. My fuel trims would just dump the max amount of fuel (+25); the motor would shudder, misfire and smell very rich with heavy soot on the exhaust openings. Keep in mind that positive fuel trims are dumped on top of your Power Enrichment at WOT as well and I certainly didn’t want all that extra fuel at WOT. I should have figured this however I didn’t realize it would be this bad. After refusing to believe just the overlap and the headers would cause this bad of a false lean condition (and subsequent maxed + fuel trims), I confirmed I had no air/exhaust leaks. Now I needed to find a way to keep my fueling stable during idle. I figured I had the choice of going full on Speed Density or do a Hybrid Open Loop approach. Here is what I did, as I chose the “Hybrid Open Loop/Closed Loop” approach:

With a big cam (lots of overlap) and long tube headers, O2 sensors (including widebands) are worthless at idle. I had two approaches that I tried. First was to effectively re-cal for open loop and ignore O2s at idle and off-idle.


Disable closed loop at idle and part throttle by setting PE TPS vs. RPM to 0 from 0RPM to 1200RPM inclusive. This forces Pe mode at idle (and subsequently Open Loop) and ignores the O2’s

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Set Pe enrichment to 1.0 from 0RPM to 1200RPM inclusive. This “prevents” any Pe mode fuel enrichment to occur.

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Also...
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Set columns 68*F through 230*F in your OL F/A vs. Coolant Temp vs. Map to 1.00 (one) up to the Map value you saw during your idle scans. For me I have a 1.00 in all cells from column 68*F – 230*F and 20-80 kPa inclusive. (HPT > Engine > Fuel Control > OL/CL > Open Loop > Eq Ratio). This is the open loop fuel adder table I showed you before by forcing ~14.7 from 140 degrees to hot idle...over-rule my suggestions and follow the next few steps Krambo has here if you are experiencing the big cam issues described in this particular section.

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Set Pe enable to a value lower than what you see at idle (look at your previous idle scans), I set mine to 50kPa and see 75-76kPa at idle (HPT > Engine > Fuel Control > Power Enrichment > Power Enrichment Pe Enable tables). In the same group of tables, set the Delay RPM and Enable Torque to Zero. I also made sure there was no “adders” adding fuel such as “Add vs. ECT” and “Add vs. IAT”. Doing all of this ensures you will actually be in Pe Mode and subsequently OL at idle.

Disable STFT Open Loop (HPT > Engine > Fuel Control > OL/CL > Open Loop > STFT Open Loop).
This is optional however did help me out for off idle transitions:

Set Closed loop proportional O2 error to (left to right):
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Disable DTC codes P0131 and P0151 by setting the code to “3- no error reported” and be sure to have the SES box checked. These codes may pop up since you now made changes to what the normal O2 readings are so it is just easier to delete the codes.

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Save the changes and Flash the PCM with the new settings.

Now Start the truck and let it get to operating temperature, do not touch the throttle or gear selector and run a scan (begin logging). Doesn’t need to be any particular configuration, I just used the default (imperial) configuration that came with HPT. Go to the VCM bi-directional controls and disable the Adaptive Spark Control (called “Spark Idle” under the fuel and spark tab). Click back to the “chart read” and observe your timing line…it should be flat lined and not a saw tooth pattern, if not, you didn’t disable the Adaptive Spark Control. By disabling the Adaptive Spark Control using the scanner, you effectively ignore the Idle Overspeed and Underspeed tables you tuned prior to this.

Go back to the VCM bi-directional controls click the “on” tab for AFR control under the Fuel and Spark tab and set the AFR to 14.7 (should by default be that). Raise this by 0.5AFR and listen to idle quality. Keep raising this by 0.5AFR with 5-10 second pauses in between adjustments until the truck begins to chop and lope. This means you have reached a lean condition and should stop there. Time to back off the AFR off by lowering it 0.1AFR at a time until you have found the sweet spot for idle quality. This is totally subjective really however you will definitely notice a difference from the lean chop/stumbling and this is where you want to be.

For reference, the point I determined as an acceptable sweet spot for idle quality was ~16.3 from the start point of 14.7 (same as the guy that coined this method). Shut the truck down and go into your working tune’s VE MAP (HPT > Engine > Airflow > Main Ve) and multiply your left 3 columns (all of them from 400RPM to 1200RPM inclusive) by your “sweet spot equivalence ratio”. For example, 14.7/16.3=0.9. Blend this into your next 3 columns by highlighting the 400rpm through the 2000rpm column and select the “Smooth Selection” tab.

Save this file and re-flash the PCM. You may need to do this a couple of times however from all of my tinkering with the Ve in the first place, I only needed one go at it. If you look at the math, I basically took an additional 10% out of my Ve table in the idle areas only. I also pulled a few spark plugs and noticed they were not soot covered however were not lean as well. Being that I was effectively in Open Loop with this procedure, the fuel trims would leave the fueling alone and the motor runs nicely and wouldn’t grow rich as it sits idling…and I could still use the LTFT for cruising.

Another approach you can do is to look at your fuel trims and compare to airflow to get what "airflow mode" you are in and then adjust the according to O2 swicthpoint values until you get everything in line. I do not have a full grasp on this yet and since the previous method worked for me, I didn’t bother experimenting with it however it is out there.

Here's my contribution for drive-by-cable engines

I recently had to tame a pair of LS1's this past summer that lead me to learn everything posted above. One LS1 in particular had a cable driven throttle body and the following is what I did to create a rock solid idle. I learned everything I know from HPTuners forum so here's me giving back. :drivin:

During your engine build, if you have a cable driven throttle body, do yourself a favor and unbolt your throttle body from your intake and use a Torx T15 bit to flip your set screw upside down. From the factory it's only accessible from underneath and it sucks to try to adjust the set screw once the engine is in the vehicle and you've got everything hooked up. By flipping the set screw upside down, you've made it possible to make adjustments to the throttle blade easier.

Once you have the engine idling somewhat ok, use the scanner to verify a few parameters. Look at IAC (idle air control) counts to see if they're in check. Why? The idle air control valve in the throttle body has a max range between 0 and 310 (usually) to attempt at holding your idle right where you command. The idle air control valve (IAC valve from now on) is designed to let by-pass air flow into the engine simply to hold idle steady and it opens/closes depending on if the computer detects the idle falling or getting too high. Most well tuned engines regardless of cam size can make use of the 0-310 range which the IAC valve has but sometimes you have to help it by opening or closing the throttle blade a little.

This is where the idea behind drilling throttle blades comes in. Don't do that yet! Thankfully you read this thread before shoe-horning your LS1 into some tight engine compartment and you flipped your throttle blade set screw over so you can open or close your throttle blade by little increments at a time. Most of us need to open it.

If the IAC counts in the scan are basically stuck at zero no matter what, that means the IAC valve is closed because it's trying to limit how much airflow is being sucked at idle. This either means your throttle body is open too much, or you could potentially have a vacuum leak somewhere and this should be addressed before continuing. Did someone previously drill a hole in your throttle body and now it's getting too much airflow this way? Assuming your seals are in working order and your TB isn't holy (:pray:) you simply need to close the throttle blade a little bit as long as it doesn't stick shut. You'll know what this feels like when you hit that "stuck" point when the blade is closed all the way - hopefully you don't hit that.

On the flip side, if your IAC counts are maxed at 310 it means your IAC valve is sucking as much air as it's allowed to and that's really the only thing holding your idle somewhat steady. :banghead: This is where you need to open your throttle blade by adjusting the set screw with the T15 bit. How much? Well...read on. There are a few parameters or "rules" for opening the set screw you should keep in mind, and you'll use the VCM scanner to tell you most of it.

Start the engine and wait until its fully warmed up. Add tps voltage to the scanner and start opening the throttle blade up with the set screw a small turn at a time as the IAC position will change slowly, hopefully dropping from 310 to below 100 counts. Adjust it so that it is 70-80 at hot idle. Keep an eye on tps voltage, as you want to keep it under .76v and this is just a rule. If it climbs over .76v before you get your IAC counts below 100, try loosening the set screw and rotating it back. You may have to drill a hole in throttle blade if this does not work, but that is the last resort.

After you have all this adjusted, turn the engine off, unplug the IAC harness and TPS, turn key forward to on (with the engine off) for 10 seconds, then shut off and reconnect everything. What this process does is it performs a TPS relearn so when you're idling without touching the gas, the PCM sees where the "new" 0% throttle position is instead of being at 1-3%.

Once this is done, let the engine cool down to as cold as possible and re-perform the idle-airflow.cfg config I attached above because now your base running airflow needs are different.

Hope that helps.

Good info

I have never seen anyone put the target idle the same across though? You have any luck with that with your cam?

Quote:

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Originally Posted by Ben Charles

Good info

I have never seen anyone put the target idle the same across though? You have any luck with that with your cam?

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I think the target idle being 850-1000 in this guide is for tuning purposes only for the initial start up to get the engine running. Afterwards I always go back and make my target idle something that starts high and gradually decreases.

EDIT: Updated in the How-to hopefully to avoid confusion. Thanks for pointing this out. Please feel free to continue proof reading this for errors as I'll be more than happy to address anything you've guys got to add.

Thanks for taking the time to post this, will come in handy when I get my car h/c

In an automatic car what causes the idle to jump up when shifting into drive or reverse? My car wants to jump forward when you shift it into drive. I have a log of it doing this just tring to figure out what to adjust to stop this.

Quote:

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Originally Posted by bigfatls6

In an automatic car what causes the idle to jump up when shifting into drive or reverse? My car wants to jump forward when you shift it into drive. I have a log of it doing this just tring to figure out what to adjust to stop this.

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Match your ignition timing in high octane, base spark park, and base spark drive. See the timing spike to 30 when you shift?

Quote:

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Originally Posted by mecanicman

Match your ignition timing in high octane, base spark park, and base spark drive. See the timing spike to 30 when you shift?

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Thanks. I matched the drive table but not the park table. should I match the whole table or just the columns up to 1200 rpm? I now have them up to 1200 rpm like the guide above shows to do.
Now I just have to figure out how to fix the "cruise" condition I have now while driving. I have tried playing with the throttle cracker and and follower some already.

just in the idle area should be fine.

Someone put a lot of time into this with the intent to help others, so don't take this wrong way, but there are some sweeping assumptions in there for sure.

Many of them are related to airflow tables. It mentions the throttle follower, throttle cracker, and adaptive idle's operation being absolute. They are in THE particular OS and revision that was written about above, but it ends there. It looks like a truck at a glance. F-bodies and Vettes will not operate the same. In some OS's, the throttle cracker (IAC cars, not most vettes) will act like a rolling idle, adding airflow whenever the enable threshold speed is passed (vehicle is moving). In many of the later OS's (including the popular '156' 01M6-02M6/A4 OS), the throttle cracker (TC from here) works when the clutch is out (car is moving, in gear, or had been put in neutral and clutch is out) but not IN. That makes it pretty useless when it's disabled at clutch in. Most all Vette's fall into this group as well. The information posted above also mentions zero'ing the throttle cracker for the purpose of return to adaptive idle [while moving]. Most car OS's do not return to adaptive idle until the car is stopped, so what is there in the TC may be irrelevant.

What it SHOULD tell you is to use the idle cfg and go out and SEE what your particular car/OS does in these situations. See WHEN adaptive idle comes and goes firstly. Do this by watching the STIT's. When they stop, so does adaptive idle. If you have an automatic car, the TC is almost certainly active when the car is moving. Just a tip, if you have cam surge, make sure you don't have the spot with buck on the TC loaded up with airlfow. If you have an M6 car, it's important to know for sure when the table is used. Go log, and watch the TC values to see what they add. Try clutching in and see if the TC zero's or continues.... while you are at it, glance back at adaptive idle just for grins through both clutch in and clutch out as well, so that you know for sure when it's operational and when it's not. While going through your log, pay attention to the throttle follower (TF from here). Many times, return to idle issues on IAC cars are caused by a TF that hangs on too long. With the car sitting still, rev and release. Watch the follower decay as the revs fall back to idle. If the follower decays too late, the idle RPMs may fall below the idle set point before adaptive idle can begin working. If the follower decays too soon, adaptive idle will begin to early, and the STIT will be pulled artificially negative. The programming does not consider the fact that 1600 RPMs at zero throttle could be different in a return to idle scenario vs. just an unusual high idle. To counter what it perceives as a high idle, it can pull the STIT too far negative, and the car will dip below idle set point or worse; stall. The point with explaining this is that the TF, TC, and adaptive idle operate differently between different years and OS's, and the only way to know for sure what you have is to do a little logging and see.

There are more things that are in similar fashion, it's just all I have time for at the moment.

Frost I think you bring up a separate, unintended point here. I believe more tuners, myself included in certain areas, need to learn how to use the scanner more efficiently. The scanner has a wealth of information to tell us and I feel like a tutorial in how to use some of it's most important functions should be added to this How-to....hint hint lol. :D

Quote:

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Originally Posted by Rinkrat456

Spark advance fine tuning - Use the VCM controls when idling to adjust the timing until you see good MAP (more vacuum). I turned off adaptive spark using the bi-directional controls with the scanner (Spark Idle) so I had a steady, flat timing line and could actually see if there was MAP changes. Do this by going to the VCM bi-directional controls and disable the Adaptive Spark Control (called “Spark Idle” under the fuel and spark tab) by actually clicking the “ON” button. Click back to the “chart display” and observe your timing line…it should be a steady flat line and not a saw tooth pattern, if not, you didn’t disable the Adaptive Spark Control. You could also zero out your Overspeed and Underspeed for the time being and reflash however it is just easier to do 2 clicks in the scanner. O.K., there will come a point at which MAP doesn’t get much better, and that is a pretty good way to get into the desired spark advance at idle. Listen to your engine for idle quality as well. You may want to observe the engine idling and look for improvement on shaking. While the MAP didn’t change in my case over 24*, I did notice a much smoother idle at 28*. If you get some idle surge, chances are you may have too much timing in there (if your base running airflows are tuned and your fueling is good). Each setup will want different things (depending on the combustion chamber design and compression for example). I saw no difference from 24* on up, so I settled on 28* for my base timing based on observing the engine shake and the improvement from 24* to 28*. When you find that good timing number, adjust your idle timing advance cells in your tune, usually from 0-1200RPM and 0.08 – 0.28 g/cyl (remember…do all the timing tables: Idles and Mains!), save and reflash the new changes to the PCM.

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I like your method for finding the optimal spark advance at idle, it works, I've done it myself...however, I disagree that you should idle right at that spark advance.

When you find the point where adding more spark advance doesn't bring your MAP readings any lower (more vacuum) you're now at the point where the adaptive controls (when you're not tuning the car and the owner is driving it) can't help catch the idle by adding spark.

I like to find that spark advance target, then lower my final target advance some...not a ton...not so much that the idle gets noticeably worse, but where these instructions decided to have the car target 28 degrees...it was also noted that going above 24 degrees didn't actually help MAP readings at all...I'd have it target 21-22...I know your perception in the drivers seat might not quite feel as smooth at idle, but it gives the PCM a fighting chance when conditions (atmosphere and fuel) change over what they were when you were tuning it.

Hey Mike,

Another note is that spark on the high edge can de-stabilize idle and cause a swing.

Quote:

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Originally Posted by MikeOD

I like your method for finding the optimal spark advance at idle, it works, I've done it myself...however, I disagree that you should idle right at that spark advance.

When you find the point where adding more spark advance doesn't bring your MAP readings any lower (more vacuum) you're now at the point where the adaptive controls (when you're not tuning the car and the owner is driving it) can't help catch the idle by adding spark.

I like to find that spark advance target, then lower my final target advance some...not a ton...not so much that the idle gets noticeably worse, but where these instructions decided to have the car target 28 degrees...it was also noted that going above 24 degrees didn't actually help MAP readings at all...I'd have it target 21-22...I know your perception in the drivers seat might not quite feel as smooth at idle, but it gives the PCM a fighting chance when conditions (atmosphere and fuel) change over what they were when you were tuning it.

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I totally agree with you. I find I err on the side of tuning idle spark advance in the same way you do. I agree, Krambo should have stopped around 24 or less.

got a question about the russk idle config. Im pretty sure i have the right one but on the histogram display only the first 2 work. 3-7 show histogram not supported with current loaded parameters. Do i need to change some stuff or what"?

im attaching the config im useing

That's not Russ Kemp's running airflow config file, but that one will work. You only need the first histogram, as the sole purpose of that config file is to dial in your running airflow tables.

Perform the process in park/neutral first. Let the engine cool down (usually I do this on a weekend and start each morning), then repeat the process in 1st gear (manual) or drive (auto) while holding your foot on the brake/clutch in.

Quote:

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Originally Posted by Rinkrat456

That's not Russ Kemp's running airflow config file, but that one will work. You only need the first histogram, as the sole purpose of that config file is to dial in your running airflow tables.

Perform the process in park/neutral first. Let the engine cool down (usually I do this on a weekend and start each morning), then repeat the process in 1st gear (manual) or drive (auto) while holding your foot on the brake/clutch in.

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do you have the russ kemp idle configuration? I would like to check it out. Is the first histogram the right one for base air? Im fixing to do a log with the above posted configuration and I post it up let me know what you think. for some reason when you first start this car up I have to give it a little gas pedal to get it to stay running but after that its fine. also a couple of minutes of idleing it will die but it will start right back up and idle fine. Not really sure what that is.

im adding a copy of the tune thats in the car and also the configuration. I added an idle log, the configuration and my tune let me know what you think I need to tweek. The airfuel ratio looks pretty good it starts out a little rich right at start up arround 12.1 or so but comes up quick to mid 14s to low 15s
Thanks,

Quote:

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Originally Posted by Frost

Someone put a lot of time into this with the intent to help others, so don't take this wrong way, but there are some sweeping assumptions in there for sure.

Many of them are related to airflow tables. It mentions the throttle follower, throttle cracker, and adaptive idle's operation being absolute. They are in THE particular OS and revision that was written about above, but it ends there. It looks like a truck at a glance. F-bodies and Vettes will not operate the same. In some OS's, the throttle cracker (IAC cars, not most vettes) will act like a rolling idle, adding airflow whenever the enable threshold speed is passed (vehicle is moving). In many of the later OS's (including the popular '156' 01M6-02M6/A4 OS), the throttle cracker (TC from here) works when the clutch is out (car is moving, in gear, or had been put in neutral and clutch is out) but not IN. That makes it pretty useless when it's disabled at clutch in. Most all Vette's fall into this group as well. The information posted above also mentions zero'ing the throttle cracker for the purpose of return to adaptive idle [while moving]. Most car OS's do not return to adaptive idle until the car is stopped, so what is there in the TC may be irrelevant.

What it SHOULD tell you is to use the idle cfg and go out and SEE what your particular car/OS does in these situations. See WHEN adaptive idle comes and goes firstly. Do this by watching the STIT's. When they stop, so does adaptive idle. If you have an automatic car, the TC is almost certainly active when the car is moving. Just a tip, if you have cam surge, make sure you don't have the spot with buck on the TC loaded up with airlfow. If you have an M6 car, it's important to know for sure when the table is used. Go log, and watch the TC values to see what they add. Try clutching in and see if the TC zero's or continues.... while you are at it, glance back at adaptive idle just for grins through both clutch in and clutch out as well, so that you know for sure when it's operational and when it's not. While going through your log, pay attention to the throttle follower (TF from here). Many times, return to idle issues on IAC cars are caused by a TF that hangs on too long. With the car sitting still, rev and release. Watch the follower decay as the revs fall back to idle. If the follower decays too late, the idle RPMs may fall below the idle set point before adaptive idle can begin working. If the follower decays too soon, adaptive idle will begin to early, and the STIT will be pulled artificially negative. The programming does not consider the fact that 1600 RPMs at zero throttle could be different in a return to idle scenario vs. just an unusual high idle. To counter what it perceives as a high idle, it can pull the STIT too far negative, and the car will dip below idle set point or worse; stall. The point with explaining this is that the TF, TC, and adaptive idle operate differently between different years and OS's, and the only way to know for sure what you have is to do a little logging and see.

There are more things that are in similar fashion, it's just all I have time for at the moment.

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Hit the nail on the head... I find it most time consuming figuring out what the OS that's in a particular vehicle does as opposed to tuning the tables. Once you know when/what/if/then on a particular OS then the tuning falls into place.

The Idle programming is very complex and takes alot of tinkering and hours to truly figure out.

Quote:

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Originally Posted by LSxpwrdZ

The Idle programming is very complex and takes alot of tinkering and hours to truly figure out.

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now that's the truth! :cheers:

I believe I have read somewhere that some disable the Closed Loop proportional. Wondering if I should mess with this or not?

Great info..This is my first post .. I'm subscribing :)

This is a very good source of information.
I wanted this information saved as HTML for offline use, but the pictures were too large to fit the screen and the text didn't fit either so I needed to scroll over and over.

This PDF file I made is this exact same information but with a little formatting and cropped/resized pictures to fit the screen for easy reading.

Thanks for sharing this information.

Here is the file if anyone wants to have it for offline use.

Change .hpt to .pdf file extension

Thanks for the conversion...looks good. I can echo Frosts' strategy to idle/return to idle tuning. I have spent hundreds of hours logging various parameters and seeing how the react/effect idle quality. Large cams make the situation even more challenging. Very frustrating at times as you think you get it figured out and make changes and then...no effect, or worse :-(. The secret is don't give up on it. My biggest find several years ago was RussK Idle .cfg approach, the rolling/clutch in TC/TF operation in my vette and end of injection timing.

The Gen III PCM/OS's require much more "attention" than the Gen IV's. Keep up the efforts and don't get frustrated. Your end result when right is a great feeling.

Ed M

Quote:

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Originally Posted by mowton

RussK Idle .cfg approach, the rolling/clutch in TC/TF operation in my vette and end of injection timing.

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Ed

What are you doing for rolling/clutch in TC/TF adjustments and logging?
Thanks
Sarge

Quote:

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Originally Posted by SargeZ06

Ed

What are you doing for rolling/clutch in TC/TF adjustments and logging?
Thanks
Sarge

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Sarge,

I wish I could say I have the Holy Grail of idle tuning, but it seems it is different for every setup. The following is how I go about it and in no means is the only way. The ultimate goal, at the 50,000 ft level is to get all the critical parameters like LTIT/STIT, VE/MAF, RAF and Timing (both idle and main) as close to zero as possible so as you depress the clutch the engine returns to idle conditions without the aide of Adaptive idle (timing/air control) or TF/TC. Depressing the clutch to my mind is the same as a quick transition to idle....only moving. There is no zero throttle load/decel coastdown effects you would see in an Automatic setup where the TF/TC would come into play. To me it is the same as trying to establish idle without Adaptive Idle Control while rolling. HPTuners has even provided several tables in the Beta Version which allows you to set the rolling idle air, rpm and TC/TF elements. I jave played with them a bit, but consider them to be a crutch and am determined (or stubburn) to do it the old fashion way.

So whether you use the base parameters or the Beta versions, the ultimate goal is to get the air and timing correct so you have the best chance return to a stop smoothly and then let adaptive idle take over. This of course is my theory and any semblance to reality is purely coincidental ;)


Some key elements include:

If car has non-stock Throttle Body, set the Scalar (DBW) or IAC Effective area tables (DBC) accordingly. You will have to set the RAF to bring in the LTIT/STIT. The goal is to get the LTIT as close to zero as possible. I try to get the best idle condition without over/underspeed correction. Set the idle timing to give you the maximum vacumn (lower MAP kPa) and then back off 4-6 degrees. Run RussK idle .cfg to set RAF; may need to do it several times.

Set the idle and main timing tables to the same values from 1200 rpm and down and say .12 to .04 g/cyl. Idle timing should not be set to MBT so you can have a bit of plus/minus from the under/overspeed correction (see above). Base timing (used in the coastdown) should be set to MBT to provide the best stability as you are transitioning to a stop/idle condition. Smooth the main table into the idle area. Set timing in 400 rpm column a bit higher to increase torque to fight through an RPM sag.

Tune the VE/MAF as close as possible to zero error (open loop) in the idle area's by working backwards from say 1200 rpm.

Tweak RAF at any problem area's just short of "cruise control" levels. No science here...trial and error.

Well that is my limited thoughts on tuning the idle/return to idle on Gen III manual vehicles. Look forward to any other opinions/strategies especially on large cam vehicles. My quest for perfection has really never be reached, but does come out very good.

Ed M

Seams reasonable enough to me. ^^^

I'm going to borrow the tip of VE tuning around idle areas by raising idle with the scanner to 1200, and back it down to as low as possible. This way you're not trying to dial in those 800-1200 cells by driving around, probably only hitting them a handful of times to get your average. With mowton's tip, you can use the scanner to raise the idle and dial in the VE from 600-1200 easily. Once the fueling is within spec, move on to spark tuning in the same fasion. I like it!

Usually if I can get the idle down to a stable 600rpms on big cam'd cars and trucks, I know I've done my job as a tuner and can rest calmly. Afterwards I'll ask the owner of the vehicle (or go by personal preference) what he or she wants the idle set at (sometimes talking them down from their desired 1500rpm idle speed) and then I'll raise the idle a bit from the 600rpm I tuned the engine to, just to make the exhaust note sweeter. :D

New to GM & great Info. Working with a C5 Z06 w TSP 233/239 Cam .595/.603 112LSA. The Tune the car came with seems to run and idle rich and LTFTs still adding fuel. I'll give this a try.

from witch table can i adjust idle AFR

thanks

Good thread

I have a potentially dumb question about an aftermarket throttle body and the tune modifications.
If I have a cable driven aftermarket (Fast 90mm) throttle body and intake, what tables do I need to adjust to make sure that everything is calculated correctly?

Quote:

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Originally Posted by abdulroof-alkhoja

from witch table can i adjust idle AFR

thanks

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MAF and VE

Ed M

Thanks for the time and information in this post.
I’m curious as to why you lower the O2 sensor switching points in the big overlap cam section to lean the idle when you already have the car in OLSD up to 1,200 RPMs? It would seem that to O2s are out of the picture below 1,200 RPMs. Wouldn’t that cause the properly tuned car to go lean at part throttle cruising speeds above just 1200 RPMs?

Quote:

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Originally Posted by 99LS1SS

If I have a cable driven aftermarket (Fast 90mm) throttle body and intake, what tables do I need to adjust to make sure that everything is calculated correctly?

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What is the correct way to adjust idle for a 90mm tb?

Also interested in the post by Sunny.

??

This thread was outstanding for us struggling with rich idle.
My issue was 12.3 AFR @ idle, found that the idle grams were about 4 high across the scale. I did the cfg scan from cold, copy and pasted to the idle air chart and brought it to 15.2. Then lowered to the final of about 7.1 grams to get my 14.6.

Thanks again for helping / posting up this!!!

My first post here on HP tuners. In the process of idle tuning my 04 GTO. I have followed this step by step as a guide but have a question. I dont this step- add 4º of idle timing 1200 RPM and under and 0.08 – 0.28 g/cyl inclusive (HPT > Engine > Spark Control > Spark Advance > Idle Spark Advance (in Park).
Later it says to Make sure that your Idle Spark Advance table (both “In Drive” and “In Park”) match your High and Low Octane Table for all columns up to 1200 RPM (HPT > Engine > Spark Control > Spark Advance > Idle Spark Advance (in Park, in Gear), Hi and Lo Octane). Blend the timing numbers into the 1600 RPM+ columns so there are no huge numerical transitions.

Am I just copying and pasting from the Idle Spark Advance (in Park) table to the other three. Then smoothing all colums and rows from 1600 rpm. Im probably overthinking this but i want to make sure I did it right.

Thanks