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Reply To: 04 gmc envoy 5.3l

Nightflyr *Richard Kirshy

    You state your running high positive (adding fuel) trims which actually means the engine is actually operating lean.
    If, by your statement ” wouldn’t the plugs not firing good cause the stft and Ltft not to read correctly, due to the un burnt fuel going past the o2 sensors ”
    That situation would tell the ECM that there is an excessive amount of fuel, in which to correct that would be taking fuel away (negative fuel trims)

    I would think if the plug(s) are your issue to that extent.
    You would be see / feeling it in the operation of the engine.

    You do understand:
    Higher( + 10% and above )fuel trims indicates a lean condition
    Lower ( – 10% and below )fuel trims indicates a rich condition
    What your stating in your last post is opposite to the actual operation of the fuel mapping system.