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No idle, misfiring under 2k rpms. Ongoing problem for 3+ months

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    No idle, misfiring under 2k rpms. Ongoing problem for 3+ months

    My swap has been having problems for the past 3 months and I've tried everything I can think of to try and fix it and I've spent absurd amounts of money just trying to get it working right.

    It starts up OK, then will stumble and die instantly unless I keep it alive with the gas. Even then it misfires under 2k RPM's but pulls hard above.


    For about the first 15 seconds when I start it up when its cold (morning) it will idle and not misfire, but then very quickly it starts misfiring and not idling.

    It's essentially an m50 with an m52 bottom end. OBDI Harness from a 95 m3, red label 413 ecu unmolested, 21.5lb injectors (pink tops). Had exact same problems with 17lb (green tops).

    Things I've done/replaced etc:
    New o2 Sensor
    New Cam sensor
    New coolant temp sensor
    MAF/ECU/TPS tested in another car
    New(er) injectors
    New coil packs
    Tried 3 different ICV's
    New alternator
    New walbro 255 fuel pump
    Replaced every vacuum line/intake boot
    2 different rebuilt VANOS units
    Cam timing been checked 3 times
    New FPR

    I really just don't know what to do anymore, any help is greatly appreciated in finding the problem to this. It is literally driving me crazy.
    Last edited by Knoepfler; 06-22-2011, 03:19 PM.

    #2
    fuel pressure been verified as OK?
    smoke test for vacuum leaks?
    has any water infiltrated into sensitive areas?

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      #3
      Have you tried a different DME.
      Which coolant temp sensor did you change.

      Did it ever run right before?

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