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Thread: 08 Cobalt SS Cold Start Misfire Help?

  1. #1
    Potential Tuner
    Join Date
    May 2024
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    Michigan
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    08 Cobalt SS Cold Start Misfire Help?

    I apologize in advance if I am asking too much here. This is my first post, and I have spent some time looking through threads for while and learning some things. I am not so much interested in tuning anything myself as I don't know anything about it.

    I have had the MPVI3 for a few months now. I got it for ZZP to tune my LNF. When I first got the car it had various codes that I have been tracking down and fixing one by one. Everything seems okay for the most part, except I have a rough cold start that I can't be sure was happening prior to the tune. I sometimes get codes for misfires on each cylinder, plus the random misfire code. Often times it doesn't throw a CEL, it just shows it as a pending code with my other scanner I keep in the car. But, it is obvious on cold starts after sitting all night.

    Its a 2008 LNF with 98k miles. The only mods to it are a K&N drop in filter, Powell oil separator, 3 bar MAP sensors, and ZZP high flow catted down pipe. Tuned to 93.

    On the cold start, it misfires, but then really doesn't misfire once it is warm. Again, I am new to this, so hopefully I am going about this the right way and don't catch too much hate for this ask. While I do the other diagnostics on it, I was hoping someone could take a look at a log from this morning that covers from a cold start through a 45 minute drive or so, and maybe someone can tell me if there is something obvious in the logs I am missing and if I should have someone who knows how to do this stuff modify anything. Worth a shot, plus I enjoy learning about this stuff.

    I should add that after ZZP tuned it, my car would actually stall on cold starts a few times then run fine. I contacted ZZP and they turned back on the cat warm up and since then it doesn't stall, just misfires. I have replaced some sensors, the HPFP recently, it has new plugs (but not coils), among other things. I don't really know what is relevant to know here?

    I appreciate anyone that might be willing to take a look.
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