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Thread: Feels like a misfire but no misfire

  1. #1
    Tuner in Training
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    Dec 2020
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    Feels like a misfire but no misfire

    Hello,

    I've been trying to figure out a problem I'm having under med/heavy throttle. Truck is a 6.2 with 6l80 (E38/T43) with turbo, built trans and converter. The truck feels like it has a heavy misfire but there is no misfires in the logs I have. I'm seeing some weird variances in timing but don't know what is causing it. I see in the log that right before the "misfire" the delivered torque is greater than engine torque. Is that the issue? Timing flips wildly from 14.5 to -4.8 to 13.5 two different times in the span of about .5 seconds.

    Any help would be greatly appreciated. Thanks!

    Screenshot 2024-01-07 160535.png
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  2. #2
    Senior Tuner edcmat-l1's Avatar
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    Aug 2006
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    It does look at times like you may have a misfire or more than one. Also, right where you've highlighted in the screen shot, you're in PE but it goes dead lean. Also looks like it may have lean popped in the intake.

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  3. #3
    Senior Tuner
    Join Date
    Nov 2006
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    2,742
    This looks like it was lean in the situation you took a snap shot of.

    Using a MAF in this situation will have you running rich/lean in odd mid/half throttle spots like this. I'd recommend redoing it in SD.

    You got to get a wideband on it ASAP. I recommend the AEM Can bus version.
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