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Thread: Car misses idle on clutch in, need some fresh ideas

  1. #1

    Car misses idle on clutch in, need some fresh ideas

    What are some ideas to cure a car from missing idle on a clutch in. Many times when I clutch in while driving, the car will miss idle and I'll have to tap the gas to get it to catch or it will die. It is especially bad when I'm off the gas and slowing down. If I clutch in, it will almost certainly shoot past idle.
    I'm not sure if it's a spark or air issue. It would seem throttle follower is the answer but I'm not sure. I havn't yet taken the decay rate down to the lowest value but I do have it pretty low, like .0020, and the IAC still closes too fast for it to catch. I wish there was a way to get the IAC valve to close slower the closer it got to the idle count value. I heard ramping up timing around the idle spark area in the base idle spark tables would help to slow the return to idle but I havn't had much luck with that yet, perhaps I just need to fiddle with it more.
    One thing is for sure, I've had nothing but problems messing with throttle cracker. It seems it would help if it didn't cut down to 0 when you push the clutch in. I can't even back out of my driveway with out the car dying several times if I have throttle cracker enabled. I'll be backing up with the clutch in and as soon as I push on the brakes, the idle just free falls to 0. I even put in 8g in the 400rpm column and it did nothing since throttle cracker doesn't work with the clutch in. With throttle cracker disabled, the car backs up with a rock solid idle. I tried uping the throttle cracker values a bit in the 800-2000rpm columns too but it didnt help either with the backing up thing.
    Could messing with the time delay on the 5 items under Idle RPM>Adaptive Idle fix this?
    What am I missing or what have I done wrong or not messed with enough?
    I need a new perspective!
    Thanks
    -Chris

    P.S. I'd like to solve this without throttle cracker if possible, if it's not, then I guess I'll have to use it somehow!
    Last edited by jimmypop13; 12-14-2009 at 12:06 PM.
    2016 Camaro SS
    Full exhaust, rotofab CAI, ported IM/TB, E85, 3600rpm stall TC

  2. #2
    Tuner KFZ)^'s Avatar
    Join Date
    Nov 2007
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    San Diego, CA
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    90
    I see you have Ford 42lb injectors. Do you have the correct fuel injector values? Those injectors are popular for use in LSx GM engines, but until the recent DVD came out with the correct values, many folks have been running their cars with incorrect values in their tunes. The work-around is to use adjusted airflow values, but it is like a band-aid instead of the truly correct way to fix it. Just a thought.
    2001 Corvette Z06

  3. #3
    Quote Originally Posted by KFZ)^ View Post
    I see you have Ford 42lb injectors. Do you have the correct fuel injector values? Those injectors are popular for use in LSx GM engines, but until the recent DVD came out with the correct values, many folks have been running their cars with incorrect values in their tunes. The work-around is to use adjusted airflow values, but it is like a band-aid instead of the truly correct way to fix it. Just a thought.
    i have the correct data
    2016 Camaro SS
    Full exhaust, rotofab CAI, ported IM/TB, E85, 3600rpm stall TC

  4. #4
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093
    Tune and log?

    IAC isn't normally the issue as it doesn't react fast enough for changes. It is almost always spark.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  5. #5
    I don't have a log at the moment but can you read beta files? Since I have an 09 HHR SS too, I have to run beta. Not sure if you remembered that or not.

    Here's a tune file
    2016 Camaro SS
    Full exhaust, rotofab CAI, ported IM/TB, E85, 3600rpm stall TC

  6. #6
    Potential Tuner
    Join Date
    Nov 2011
    Posts
    2
    up the follower air flow by a good bit to see if it will hang high then you know your on right track