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Thread: Idle Help

  1. #1
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    Idle Help

    I have just installed a 408 with a FAST truck intake, 46 lb/ hr injectors and 102 mm throttle body. I am having some trouble at idle. Specifically, I have to hold it at about 1400 RPM to warm it up. Once it is about about 130 F it will idle correctly. I believe the IAC does not do anything until it gets this warm which I think is odd because it should be active immediately. Please take a look at my cal and give me some input. Thanks.
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  2. #2
    Tuner 1slowbusa's Avatar
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    Your base running airflow looks really high. I have a LS1 with fast 102 and 102mm TB and all my values are

    2.9101 2.5133 2.0106 1.6138 1.3757 1.1375 0.9789 0.9391 0.9391 0.9391

    Yours is
    6.6748 6.6282 6.5812 5.4550 4.4153 3.5900 2.6419 1.6940 1.1667 1.0608
    2000 Camaro SS
    Polluter V2 Cam
    AFR 205 Heads
    Fast 102 Intake
    & More

  3. #3
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    With the LS1 use Russ K's Idle Cfg. First get your air closer to what was posted for you there. Then use Russ's cfg to get it right. You will make sure the engine is dead cold, then start the scan before you even start the engine. The data you need is in the #1 histo and make sure you set the data to Last Value, not Average Value for this. It is a simple copy/paste of those numbers from the histo to your tune and you'll be nuts on bud. Do not touch ANYTHING during the process either. Let it go from dead cold till your fans kick in and use the data you get to set your RAF Table(Base Airflow Table)
    I make LS1's idle better than stock with Russ's cfg
    2000 Trans Am WS6

  4. #4
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    Idle help follow up

    I really appreciate the guidance. I was not able to work on the cal until yesterday and today. I followed the steps above I believe to a T. My shop was about 68 so I started recording data at that temp for the IAF. I copied those data points directly into my cal. The config file only had one decimal place so I didn't have the normal 4 decimal places of accuracy, but I don't think that ultimately mattered. If I am wrong, please let me know. The numbers I recorded by collecting data from the config file were:

    2.20002 2.16927 1.85860 0.89998 0.50004 0.70001 0.79999 0.79999 0.70001 0.70001

    With the lower IAF numbers from the config file it did seem like it wanted to start fairly well. But the numbers provided as a starting point:

    2.9101 2.5133 2.0106 1.6138 1.3757 1.1375 0.9789 0.9391 0.9391 0.9391

    seemed to work even better. So I went back to those. It also seemed like it may have needed some more cranking fuel so I increased both tables 10% to try and help it start.

    Today I drove it. When it is cold, you still have to put your foot in it for a while to keep it running around 1400 RPM. It seems like it wants to start on its own without sticking your foot in it, but it just won't run. After I put it in reverse it would back up a ways and then die. It would generally start well after that, but almost always it takes two cranking events to start - this is after it is hot. Is the added cranking fuel causing this? I don't know. It will idle sooner on its own now than it did before which is of course nice. As a general rule, when I drove it, it would come to an idle (too slowly I might add) and then die. I ultimately increased the airflow several times up to:

    5.15546 4.45261 3.91820 2.85895 2.43731 2.01529 1.73446 1.66393 1.66393 1.66393

    This is a lot more than what was suggested to me. However, it does seem to help. It still doesn't start right and will take two crank events to start (with no TPS required when hot). If you come to a stop fairly quickly it will die. I have not messed with the PID for for the idle. I have a feeling that may need some work too and that possibly the problems there are overlapping my idle air problems.

    I should mention this has a lot of camshaft with 110 degree lobe separation so there are a lot of dynamics going on in the intake.

    I have attached my latest cal and some data for review. I appreciate your help.

    Thanks,

    Ken
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  5. #5
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    Whats you cam specs (approx)? Are you using a wideband? Still have narrowband O2 sensors? Is your MAF connected? If it is connected, it looks to me it is not disabled in the tune. If that's the case it hasn't been tuned at all and it needs to be. Also the VE looks way way too rich.

    The fueling has to be at least close before honing in the idle airflow.
    2001 Pontiac Trans Am M6 "cam only"
    228/232 110 cam, 10° overlap @.050" lift
    Edelbrock stepped headers, ORY, hooker catback

  6. #6
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    I don't recall the specs right now. ABout 0.594" lift and 110 of lobe separation. The MAF is connected. The VE table may be way too rich as well. I have altered that, but I am not really trying to tune the upper end right now. I just want it to idle right.

  7. #7
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    Your IAC counts are pretty high there. This is a "Drive by Cable" set up? Take the set screw and invert it for your throttle. Using the scanner, then open the blade to 2% using the set screw. Reset the TPS by unplugging it and then key on, off and plug it back in. Check your scanner and make sure it now reads 0% again. Then redo the idle cfg and enter the resulting numbers given from Russ's cfg. You need to get those IAC numbers down. Then you should be able to get a better idle out of it. Step one here is to get the IAC's down from what Im seeing
    2000 Trans Am WS6

  8. #8
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    Thanks. I'll give that a try next.

  9. #9
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    So I gave that a try. I first reset the TPS 2% higher and then zeroed it as stated and confirmed it as suggested. I entered a cal that had values for the IAC that were recorded in the config file as stated below because I was thinking that with the TPS increased it should require less air.

    2.20002 2.16927 1.85860 0.89998 0.50004 0.70001 0.79999 0.79999 0.70001 0.70001

    It would start but not stay running unless I stuck my foot in it.

    So I thought I had nothing to lose so I repeated the TPS increase another 1.6% and reset this as zero. Thus I should have a total of 3.6% in it now. It still wouldn't start and stay running. So then just to see if increasing the IAC position would help, I re-flashed it with my numbers that had worked ok (but not that well):

    5.15546 4.45261 3.91820 2.85895 2.43731 2.01529 1.73446 1.66393 1.66393 1.66393

    That would allow it to run but I still had to stick my foot in it to get it to run long enough so it would idle.

    I took it for a short drive. When you put it in reverse and let it back up on its own with 0 TPS it does ok. Meaning it will hold the idle RPM. If you give it some TPS and then back up and come to a stop it will die. I did notice that there is a little less hang time at a higher RPM when you are at 0 TPS with the throttle blade opened further with the set screw. So this may be going in the right direction. I am open to suggestions of course, but I wonder if the 3.6% TPS is really enough? I wonder if I don't need a lot more. I should mention I never calibrated the throttle blade position and the TPS when I put the TPS on it. I suspect that is where this may have gone all wrong, but I lack the experience. I can of course keep trying to see if this helps, but I am sure some of you have experience with this already. Thanks.

  10. #10
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    Well, I would say you've gone as far as I would go with the set screw. Sounding like you are one that needs to drill the blade, it does happen! Is there a hole already in the throttle body that you've installed? If your needing to drill, you will return the blade to an actual dead stop in the body, and then start small. There is a thread here on drilling a blade to obtain idle. Ill have a look around and see if I can find it and link it here for you in case you need it.
    Before I go any further with the drill recommendation, can you check to make sure that your scanner is set to the same units as your tune? Sometimes this gets mixed up and can make things obviously all wrong when doing the RAF(Base Air) Russ cfg.
    Last edited by MMGT1; 03-19-2014 at 08:52 AM.
    2000 Trans Am WS6

  11. #11
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    Well, the scanner and tune dislay in degrees F but the scanner does not display the units for flow of lb/ min as seen in my tune. I would assume they are the same units based on the temp.

    I previsously had a GM Hot cam in my 4.8L and I had to drill the throttle blade out to make it work at idle. This seems like a logical next step.

    Thanks again.

  12. #12
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    Then you know what your into. Just get the throttle back to a natural park position, reset the TPS again, then start small with the drill until you get those IAC counts down to an acceptable level. Once you have that then back to the RAF tuning. There is only so far you can take the TPS sensor before it messes up bad. I would not go any further than what you have already done, just my opinion though. I would be moving to the drill myself at this point
    2000 Trans Am WS6

  13. #13
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    Ok. thanks. How does a 1/4" hole sound for a starting point?

  14. #14
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    I would "err to the side of caution myself". 1/8" and work up from there
    2000 Trans Am WS6

  15. #15
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    I ended up staring with a 3/16" hole. It was an improvement, but not the fix. I upped it to 1/4" and that made it better, but it still wants to die when backing up and coming to a stop. It definitely starts easier both cold and hot, but I'm not quite there yet. i am going to up it one more dirll size to 9/64" which is about what I did on my 4.8. I don't plan to go bigger than that because I think I can fix it with the software from that point I hope.

    I have a couple of related questions. I think I need to increase my fueling to match the added air for start up so I was thinking of richening up my VE table in the idle areas. Does that seem like the right path? I was thinking of doing this to help it start and stay running.

    Second, there is definitely an issue with it coming down to my set idle when I drive and come to a stop. It wants to idle at about 1600 RPM and then slowly drop to my set point. I think I need some of this hang time to prevent it from dying, however there is too much hang time. What you would suggest to alter to try and take some of this out, but not have it die?

    Thanks.

  16. #16
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    Decay Rate, see if the decay rate will help before drilling any more
    2000 Trans Am WS6

  17. #17
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    Idle Help

    So, I followed your advice and did not increase the drill size. I played with decay rate. I think that helped. It definitely starts better both cold and hot. Cold still needs a little help from my foot to get going, but it will idle on its own soon after I start now so that seems as if I'm heading in the right direction.

    Now let me discuss a new dilema. After it is hot (190 +) it will idle at about 1400 RPM. After I drive it and put it in park it will typically try to go to the set point of 800 and then fairly quickly increase to the 1400. Sometimes it goes through a unstable/ hunting pattern trying to get to the 1400. I should mention there is nothing special about 1400, that is approximately where it wants to idle. To fix the hunting, I have to shut it off and re-start it and it will idle but at 1400. After I do this restart it tries to idle at 800 as commanded for about 2 seconds and then it speeds up to 1400.

    When I start it cold, it starts fairly well as I said above. It warms up and idles at the values in my commanded table as best as possible. As a general rule I am happy with how this works. As it gets hot (thermostat working) I have had it speed up a little and then die like it has some unknowns in the table. When I start it again, it will run.

    When I put it in reverse or drive, it works perfectly and tries to idle at 800 as it is commanded. It does a fairly good job of controlling this now as well. Note that I reverted the follow cracker to the factory setting and it works much better - big surprise. I also reverted to a stock 6.0L VE table.

    I would appreciate it if you would look at my attached current cal and see if there is something obviously wrong that would make it want to idle high at the higher temps. I have looked at the IAC commanded vs actual position as this occurs and it is commanding 0 and at 0. It is not clear to me why the added hole in the throttle body causes a problem when it is hot and in park. I didn't purposely change anything to make this act this way. I have tried several of my previous cals and they all seem to have the same issue.

    Thanks,

    Ken
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  18. #18
    Senior Tuner Russ K's Avatar
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    If your IAC is 0, then you drilled too big a hole in the throttle blade. You can try backing of the stop screw first.

    You IAC counts were perfect in post #6.

    Russ Kemp
    Last edited by Russ K; 03-23-2014 at 02:10 PM.

  19. #19
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    I can try backing off the screw now, but it is barely holding the throttle blade open.

    Why am I only seeing the problem when it is hot and in park?

  20. #20
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    Russ,

    Any thoughts?

    Thanks,

    Ken