Having issues returning to idle.

[WS6HUMMER]

I'm going behind another tuner trying to help someone out, 07 sierra 6.0 with an unknown cam. Just like the title says I'm having issues with it returning to idle, it just won't recover. COAST DOWN.hptve layout.Layout.xmlDIAGNOSTIC LOG 5.hpl I've experimented with it a lot and nothing helps. When I first got my hands on this truck, I diagnosed a very weak fuel pump, had a closed loop fault that I fixed, & needed some airflow adjustments just so it would crank without your foot on the pedal. Thanks in advance.

[GHuggins]

Looks like the added fuel flow and pressure from the now working correctly pump has added some fuel being delivered to the engine. You'll probably need to retune MAF and VE. VE appears to be most at fault from the looks of it's table? Fuel trims are -10 average with -20ish spikes at times... Just wondering if it wasn't tuned originally with a "going out" fuel pump? Compare to a stock tune in the repository to see just how many things have been altered....

[WS6HUMMER]

Keep in mind this OS goes really rich after every flash. What you see is a stock VE with some fuel pulled out in the lower RPM. I tried a stock lower MAF table and there was no difference at all.

If you saw the original VE table the so called "tuner" before me put in it you would be asking if he had a personal vendetta against the person who owns the truck.

[schpenxel]

I'm going behind another tuner trying to help someone out, 07 sierra 6.0 with an unknown cam. Just like the title says I'm having issues with it returning to idle, it just won't recover. COAST DOWN.hptve layout.Layout.xmlDIAGNOSTIC LOG 5.hpl I've experimented with it a lot and nothing helps. When I first got my hands on this truck, I diagnosed a very weak fuel pump, had a closed loop fault that I fixed, & needed some airflow adjustments just so it would crank without your foot on the pedal. Thanks in advance.

When you say it won't recover I assume you mean it's staying too HIGH vs. going too low and not going back up?

I'd try taking the min airflow values you have at say 1200 RPM's and using those out for the rest of the table and see if that makes any difference (i.e. lower from 1400 RPM's and up down to what you have for the 1200 RPM column)

I'm not on the same ECM or engine but my min airflow table is really close to yours up until 1200, then yours shoots up..

Just an idea for something to try.

[WS6HUMMER]

When you say it won't recover I assume you mean it's staying too HIGH vs. going too low and not going back up?

I'd try taking the min airflow values you have at say 1200 RPM's and using those out for the rest of the table and see if that makes any difference (i.e. lower from 1400 RPM's and up down to what you have for the 1200 RPM column)

I'm not on the same ECM or engine but my min airflow table is really close to yours up until 1200, then yours shoots up..

Just an idea for something to try.

No, if you gas it and let off the idle dips & most of the time it dies. I assumed it wasn't getting enough airflow to stay running or closing the blade too fast. In the log I posted you can see this around 6.41, only thing is that the blade really doesn't close anymore than the 20% that it is at idle. I've got a stock tune or 2 with the matching OS# and set a lot of stuff back to stock including the VE.

[schpenxel]

No, if you gas it and let off the idle dips & most of the time it dies. I assumed it wasn't getting enough airflow to stay running or closing the blade too fast. In the log I posted you can see this around 6.41, only thing is that the blade really doesn't close anymore than the 20% that it is at idle. I've got a stock tune or 2 with the matching OS# and set a lot of stuff back to stock including the VE.

Turn up min airflow up for the 1200 RPM's and under areas. Add something stupid like 30% at a time just to see if it helps. If it starts hanging and not wanting to come back down then that's too far

Log idle adapt advance also

Is it a manual or auto? If it's a manual try seeing how far the throttle closes while engine braking

All guesses but hopefully something helps

[mowton]

The E38 idle tuning is a bit different than Gen III. Through the years I have read and experimented and this seems to have been the best way at least I can do it.

The Percent Max tables set the maximum the throttle blade will open in a stationary (brake) and rolling situation. You can isolate all the other controls by setting the Airflow Final Minimum to say all 64 g/sec and zeroing out the Proportional and Integral Airflow tables.

To set the max open in 2 scenarios....1) Stationary -- in gear, on the brake, idle higher than normal, AC/Fans ON etc. You monitor the timing and adjust the percentage up or down so your timing is "hovering" right around your desired Idle RPM (Over/Underspeed isn't being called into duty). Once you have that set, add about .2% to compensate for a cold start. 2) rolling is done the same way but in a coast down mode.

Now we bring the Airflow Final Minimum back and we pick a value based on the size of the cam....with a mid/large cam I usually start with say 14 g/sec. Populate the entire table with this value. The Proportional table can be repopulated with the stock values, but usually is too aggressive for a larger cam. Cut the stock vales in half to start. The Integral table is handled the same with an extra step at the end. Once you have cut it in half, interpolate from the 0 to the 512 rpm value and again from the 0 to the -512 RPM Integral. The process for tuning the Airflow Final Minimum Airflow table is to blip the throttle. How the rpms return to idle is the trick. If the return is quick and sagging or even stalling, then increase the table. If the return hangs or slowly (5-10 secs) returns then reduce the values. Once you have the blips responding well, add about 7-8 g/sec to the 6000, 7000 and 8000 rpm columns Interpolate from 1200 to 6000 rpm columns.

The last test is to disable the adaptive idle over/underspeed correction (can do this through the VCM Control) and see how stable the idle is. If hunting or surging occurs, adjust the Integral and or Proportional tables. Remember the Proportional will correct for instantaneous rpm errors and can cause instability if too tight. The Integral is more of an averaging contributor and can be attributed to rolling/wavy idle response. Once you have the idle airflow mode as good as you can get, bring back in the Over/Underspeed. You may have to "dumb down" their effects if you have a large enough cam. Don't want to be fighting the natural lope of the cam....causes instability as well.

Idle tuning can be very frustrating but think about what each of the control mechanisms, what they do and what effect they have on the control of idle. The E38 Idle is based on establishing a max and min blade opening and having the Proportional/Integral air controls manage the idle in between. Hope this helps....

Ed M

[WS6HUMMER]

Turn up min airflow up for the 1200 RPM's and under areas. Add something stupid like 30% at a time just to see if it helps. If it starts hanging and not wanting to come back down then that's too far

Log idle adapt advance also

Is it a manual or auto? If it's a manual try seeing how far the throttle closes while engine braking

All guesses but hopefully something helps

The E38 idle tuning is a bit different than Gen III. Through the years I have read and experimented and this seems to have been the best way at least I can do it.

The Percent Max tables set the maximum the throttle blade will open in a stationary (brake) and rolling situation. You can isolate all the other controls by setting the Airflow Final Minimum to say all 64 g/sec and zeroing out the Proportional and Integral Airflow tables.

To set the max open in 2 scenarios....1) Stationary -- in gear, on the brake, idle higher than normal, AC/Fans ON etc. You monitor the timing and adjust the percentage up or down so your timing is "hovering" right around your desired Idle RPM (Over/Underspeed isn't being called into duty). Once you have that set, add about .2% to compensate for a cold start. 2) rolling is done the same way but in a coast down mode.

Now we bring the Airflow Final Minimum back and we pick a value based on the size of the cam....with a mid/large cam I usually start with say 14 g/sec. Populate the entire table with this value. The Proportional table can be repopulated with the stock values, but usually is too aggressive for a larger cam. Cut the stock vales in half to start. The Integral table is handled the same with an extra step at the end. Once you have cut it in half, interpolate from the 0 to the 512 rpm value and again from the 0 to the -512 RPM Integral. The process for tuning the Airflow Final Minimum Airflow table is to blip the throttle. How the rpms return to idle is the trick. If the return is quick and sagging or even stalling, then increase the table. If the return hangs or slowly (5-10 secs) returns then reduce the values. Once you have the blips responding well, add about 7-8 g/sec to the 6000, 7000 and 8000 rpm columns Interpolate from 1200 to 6000 rpm columns.

The last test is to disable the adaptive idle over/underspeed correction (can do this through the VCM Control) and see how stable the idle is. If hunting or surging occurs, adjust the Integral and or Proportional tables. Remember the Proportional will correct for instantaneous rpm errors and can cause instability if too tight. The Integral is more of an averaging contributor and can be attributed to rolling/wavy idle response. Once you have the idle airflow mode as good as you can get, bring back in the Over/Underspeed. You may have to "dumb down" their effects if you have a large enough cam. Don't want to be fighting the natural lope of the cam....causes instability as well.

Idle tuning can be very frustrating but think about what each of the control mechanisms, what they do and what effect they have on the control of idle. The E38 Idle is based on establishing a max and min blade opening and having the Proportional/Integral air controls manage the idle in between. Hope this helps....

Ed M

Thank you both for the time and advice. I have it decelerating good right now thanks to your suggestions except now that it has enough airflow it wants to push against the brakes a little and creep at idle with your foot off the brake. I know it's too much airflow but I'm afraid if to take any out I feel it will go back to choking up on decel. What I did was change the the "percent max" from 2.97 to 3.55 & increase the "final airflow minimum" by 50% from 1200 RPM on down. With that being said I found out the cam specs tonight and its nothing crazy, 222/224 566/568 on a 112. Idle is set to 850 so I don't know if a stall is the cure or if I should try to trim the final airflow minimum. What do you suggest?

[mowton]

Try lowering the drive idle 50-75 rpm you should be able to idle that cam at 750-775 . Watch your idle timing average (it will be moving up and down a bit), if it is biased above or below your desired than it will tell you if too little or too much air.

Ed M

[WS6HUMMER]

Try lowering the drive idle 50-75 rpm you should be able to idle that cam at 750-775 . Watch your idle timing average (it will be moving up and down a bit), if it is biased above or below your desired than it will tell you if too little or too much air.

Ed M

Will do & post the results, thank you so much Ed.

[schpenxel]

Good deal. Ed's procedure is a big more in depth than mine (I call mine the "use big numbers then make them smaller until it does what you want" method)

[sssnake]

Airflow Final Minimum to say all 64 g/sec

Why 64 g/sec vice ) g/sec?

Do you adjust the throttle follower torque at all?

Sorry to jump into the middle of this thread but I have been struggling to get a quick return to idle. Reducing Min Idle Air causes stalls. I suspect VE at high vacum/low MAP may be the culprit but haven't been able to test the theory yet (power steering pump died - replacement has been interesting...). What I am observing is that the throttle angle, after removing my foot from the accelerator, does not go back to the idle opening percentage quickly. Rather it sits about 2% higher than idle throttle opening % and tries to adjust timing to lower the idle RPMs. Once roughly 10 sec pass the throttle opening percentage has returned to the normal idle value. The car has the original TB so I didn't think the scalar needed to be adjusted but if I do it does help - somewhat. I assume since the issue is during a large transient below the VE disable RPM that the ECM is using the VVE equation to estimate airflow requirements. Then those airflow requirements are translated to throttle angle. Am I on the right track or should I be looking elsewhere (while I can post the tune and a log, the tune is scaled and has lots of changes to support the mod for the car - tough to do a lot of investigation without a LOT of time spent). A snapshot of the log is attached.

2016-02-19.png

[mowton]

Why 64 g/sec vice ) g/sec?

Do you adjust the throttle follower torque at all?

Sorry to jump into the middle of this thread but I have been struggling to get a quick return to idle. Reducing Min Idle Air causes stalls. I suspect VE at high vacum/low MAP may be the culprit but haven't been able to test the theory yet (power steering pump died - replacement has been interesting...). What I am observing is that the throttle angle, after removing my foot from the accelerator, does not go back to the idle opening percentage quickly. Rather it sits about 2% higher than idle throttle opening % and tries to adjust timing to lower the idle RPMs. Once roughly 10 sec pass the throttle opening percentage has returned to the normal idle value. The car has the original TB so I didn't think the scalar needed to be adjusted but if I do it does help - somewhat. I assume since the issue is during a large transient below the VE disable RPM that the ECM is using the VVE equation to estimate airflow requirements. Then those airflow requirements are translated to throttle angle. Am I on the right track or should I be looking elsewhere (while I can post the tune and a log, the tune is scaled and has lots of changes to support the mod for the car - tough to do a lot of investigation without a LOT of time spent). A snapshot of the log is attached.

One thing I didn't include in the above, but is the first sentence in my training tutorial is make sure you have tuned your MAF/VE air models as close to idle range as possible. especially if you have a mid to large cam where their inefficiencies at low rpm require a reduction in VE.

Changing the scalar is just "fudging" the PCM's adaptive idle calculations and compensating for something else. The PCM needs an accurate understanding of the TB effective area so it can develop accurate MM2 predictions which eventually get converted to TPS control values. If you lower the scalar than you are saying the TB is smaller so the mm2 effective area will result in the blade be opened a bit more, if you increase the scalar, then its the opposite. Use that as a graphic for what "correct steps you want to make to simulate the same effect.

The VE is brought into correction even though you are below the threshold from what I have read so it is still required to get it tuned pretty close.

The return to idle speed vs hang is the BRAF and would indicate perhaps a small reduction (keep you changes small) and then maybe a little help from the Throttle follower torque setting.

Setting to 64 pushes it out of the allowable, it is then ignored and so only the MAX is used...a lot like setting the High RPM disable to 400 rpm's :-) If you set to zero then the minimum would be zero or blade would be closed.

You can use the throttle follower torque to help tailor the return to idle as well....soften the landing if you will.

Ed M

PS -- Its great to finally also see you are using the Version 3.0 Scanner........

[sssnake]

Thanks Ed! I began with a MAF tune and got the VE very close in any of the areas that I could generate steady load. I guess what I need to do now is find a hill and let this thing coast down it for a while (in gear) and log the results. Thanks again.

[Michael_D]

Dang. I need to revisit idle again.

Excellent idle calibration write up Ed! This should be a sticky thread.

And GHiggins injection timing too.

Gotta say, I am seeing a new trend on this board of knowledgeable tuners taking the time to explain things so dummies like me can understand. It is quite refreshing.

[BigMike42]

Check this thread out too. Idle tuning is definitely way more than just doing some stuff with base idle airflow. That is all I did at first with my car and it did not run very well. In fact, that table really doesn't matter much at all as long as you are in the correct ballpark range. Integral/proportional/spark tables are much more important.

I like using max idle area and the vcm spark controls to find my best possible idle. Max idle area is used to lock the throttle in place with no airflow correction. I like having a theoretical "best" idle target to hit with no idle corrections before I start turning them back on.

There was a lot of trial in error in this thread, so you may want to start from the last page and read backwards.

http://www.hptuners.com/forum/showth...e-half-applied

[schpenxel]

That this has to be the best info on how these cars idle that's out there

[mowton]

Check this thread out too. Idle tuning is definitely way more than just doing some stuff with base idle airflow. That is all I did at first with my car and it did not run very well. In fact, that table really doesn't matter much at all as long as you are in the correct ballpark range. Integral/proportional/spark tables are much more important.

I like using max idle area and the vcm spark controls to find my best possible idle. Max idle area is used to lock the throttle in place with no airflow correction. I like having a theoretical "best" idle target to hit with no idle corrections before I start turning them back on.

There was a lot of trial in error in this thread, so you may want to start from the last page and read backwards.

http://www.hptuners.com/forum/showth...e-half-applied

Actually, as an EFI Live user as well, I was lucky enough to have seen and followed that post. Has been my E38 Idle Tuning (and training) strategy ever since. The only thing I couldn't get my self to do was drill the hole:-)

Ed M

[BigMike42]

Actually, as an EFI Live user as well, I was lucky enough to have seen and followed that post. Has been my E38 Idle Tuning (and training) strategy ever since. The only thing I couldn't get my self to do was drill the hole:-)

Ed M

Yep, no idea how I found that post but glad I did and was able to translate it over to HpTuners. I read that thread for hours and probably spent 50+ hours experimenting.

I'm not drilling a hole either lol. Hymey was supposed to release an updated guide, but I think he has health problems. I hope he is doing ok.

[realcanuk]

Was having similar issues with idle at one time. I followed this procedure exactly and it was unbelievable how well it worked. Not saying it is the only, or best way, but definitely works and its easy to follow step by step...
Full credit to 5_Liter_Eater for the work putting it together.

http://www.hptuners.com/forum/showth...103#post136103