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Thread: Stumble and backfire when cold

  1. #11

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    are any errors being logged by the system?

    i have no tuning skills which is why i went efi.


    watermelon

  2. #12
    Join Date
    May 2018
    Posts
    10

    Default

    No, there are no error codes.

    Thanks

  3. #13
    Join Date
    May 2018
    Posts
    10

    Default

    Here is the latest. I've gone through everything again.
    1. I found one plug wire that was a bit out of tolerance and replaced it. All others ohm out fine.
    2. I've put a fresh set of plugs in.
    3. Double checked the timing and advance, and all is in order per factory spec.
    4. I did a compression check, and all of the cylinders are within 7% averaging around 175.
    5. IAC is setting around 16-17 when idling in neutral after driving and getting it up to temp.

    A/F target are still as above.

    Pump squirt is at 18% and Power Valve is at 30%

    It runs better when cold and overall drive-ability is improved, but when I accelerate hard, it still stumbles and backfires through the intake. As long as I don't put my foot in it, it drives fine.

    Any ideas would be appreciated. Thanks!

  4. #14
    Join Date
    May 2018
    Posts
    10

    Default

    Just out of curiosity today I changed the CAM setting to performance, and it wouldn't run for more than a few seconds. I set it back and then drove it around playing with the Power Valve and Pump Squirt settings. If I take the Pump Squirt down below 18% it has a hard time with normal take off. If I take it above 22% with the Power Valve set at 30% it stalls when I come to a stop and then try to take off. I can smell the fuel. If I leave the Pump Squirt at 18% and take the Power Valve setting down to 25% it stumbles and backfires under normal driving. If I take the Power Valve up to 40% it doesn't cure the stumble under hard acceleration, and it also stalls out when trying to take off from a stop.

    Other then taking the mixture back rich, I don't know what else to try to get this thing to run right.

    I bought this for better drive-ability and have yet to get there.

    MSD - Any ideas?

    Thanks

  5. #15
    Join Date
    Jun 2013
    Posts
    6

    Default

    Hi.
    Why is the timing in "disabel"?
    You have an ignition box, why not let the ATOMIC take control of the timing?

    I'm pretty sure this will fix you'r problem.
    My advice here would be advance the timing a bit more, but with a manuel adjustment it may not be good in other driving cicumstances.

    With ATOMIC you now have the exact fuel/air mixture and remember that a LEAN mixture burn much slower than the one ritch U get from a carb.
    Thats why the vaccum advanses as much as 20 degress in some cars.

    Good Luck
    Last edited by kenta; 07-13-2018 at 01:59 AM.

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