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Thread: IDLE Misfire

  1. #1
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    Default IDLE Misfire

    Got an LS6 that misfires on all cylinders at idle, as soon as you touch the gas the misfires stop.

    I am monitoring the misfire with the scan tool, the idle misfires are enough to light the CEL (P0300). This motor has new coils, and wires. I have just added headers and a new exhaust system, the motor does need to be tuned but I am not sure why I only see misfires at idle.

    Could bad idle tuning cause these misfires? Idling around 800 rpm.



    - 2002 LS6, about 2000 miles on fresh motor.
    - 226, 229, 585, 575 116 LSA Cam
    - 85mm MAF

  2. #2
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    Are you in running open or closed loop?

    Are you running MAF only, SD or MAF/SD hybrid?

    Post your current tune and log.

  3. #3
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    Quote Originally Posted by statesman View Post
    Are you in running open or closed loop?

    Are you running MAF only, SD or MAF/SD hybrid?

    Post your current tune and log.
    Pretty stock closed loop tune.

    Forgot to mention 30lb injectors.

    I also noticed that when the car warms up, it idles around the 12s AFR, as soon as I hit the gas AFRs appear normal.
    Attached Files Attached Files
    Last edited by pormgb; June 7th, 2015 at 01:54 PM.

  4. #4
    Joe (Moderator) joecar's Avatar
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    Did this just start happening out-of-the-blue, or did it start happening when parts were replaced, or was it already happening (since it was tuned)...?

  5. #5
    Joe (Moderator) joecar's Avatar
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    BTW (unrelated to thread): your PE table at EQR 1.75 will cause engine to bog down when PE enables.

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    Quote Originally Posted by joecar View Post
    Did this just start happening out-of-the-blue, or did it start happening when parts were replaced, or was it already happening (since it was tuned)...?
    The misfires have always been there, always had P0300, changed all ignition parts but still had P0300.

    I just noticed the rich idle but it doesn't always happen, it seems to happen when the car has fully warmed up.

    I initially thought it was something to do with plugs and wires but there is no way I could have the problem on both banks of cylinders, I have dual WBOSs and they both read 11s to 12s.

    I get the 11s and 12s when idling hot, when coming to a stop, sometimes the car almost stalls. When I first drive the car its fine, as it warms up the problem occurs.
    Last edited by pormgb; June 8th, 2015 at 02:19 AM.

  7. #7
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    Quote Originally Posted by joecar View Post
    BTW (unrelated to thread): your PE table at EQR 1.75 will cause engine to bog down when PE enables.
    Ok, that can be changed.

  8. #8
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    What spark plugs are you using and what have you got them gapped at?

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    I am using NGK V-Power TR-55 Spark Plugs gaped at .40.

  10. #10
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    Can you do a log of a drive and include,

    RPM
    MAF
    MAP
    LTFT's
    STFT's
    ECT
    IAT
    VSS
    TP
    VOLTS

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