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Thread: Bad ECU?

  1. #31

    Default Bad ECU?

  2. #32

    Default Bad ECU?

    Can get IAC and O2 sensor tonight, any idea if replacing them will affect warranty or MSD's ability to diagnose. In other words would it be better for me to wait to see what they say? Absolutely will not hold you to this, in no way will I hold anyone responsible for advice given here. Just wonder what best course is. Really wonder about IAC motor as others have had problems and mine is all over the place. fcsallan any thoughts on this since you seem to be the man when it comes to IAC from all of my forum searches. Is it normal for IAC to rise with truck in gear under certain circumstances or is this screwy?

  3. #33

    Default Bad ECU?

    Does not appear to be the IAC. Replaced and no change in behavior. Thinking I need a RMA.

  4. #34

    Default Bad ECU?

    Yes, I would wait for MSD to chime in here or call their support line. Sometimes they will work with you over the phone to help diagnose the issue if you can be at your car or set up a time when you can. The other option is to get the RMA and return the handheld, throttle body and power module.

  5. #35

    Default Bad ECU?

    May have been O2 sensor! Replaced it and things seem MUCH better! Also may have found minuscule leak in header flange gasket at high temp, hard to tell because temp is high and water/soap evaporates very quickly but I think I saw a bubble or two, no leak at startup for sure. Bought a set of Percy's seals and going to swap them out and go for a drive. Even with leak, lean values have disappeared. Learn still turning off and on randomly at idle, but less than before. Still not sure what that means. Thanks for all of the help. Will post an update later after a few miles.

  6. #36

    Default Bad ECU?

    Holy #@*%!!! What a difference! Replaced O2 sensor and Header flange gasket and it is night and day (still holding my breath)! Not sure minuscule leak affected it, unless somehow it burned up sensor. Light rain here and I cant even give it 50% throttle without rear end breaking loose (35 inch tires on 20 inch rims 4:11 gears). Cruises on interstate 70 mph at 3k, before was 3.3k or more to achieve that speed! No hesitation anywhere in acceleration curve, did have to dial down to 32* total timing as it would begin to ping at WOT up a REALLY steep hill. Seems to be learning really quickly, possible that would have worked itself out given enough time. Updates to follow.

  7. #37

    Default Bad ECU?

    Glad to hear that its working better.

  8. #38

    Default Bad ECU?

    Leaning will be off when ECT is below 160°F or if any Error C codes are present.

    When the fuel pump type is in PWM mode, the system pulses the fuel pump to control fuel pressure.

    When the IAC counts go up approaching 100 or more there should be a very noticeable vacuum sound coming from the throttle body. Do you hear this? If not, the IAC may not be functioning properly.

    What are the firmware versions in your system?

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