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Thread: Help with fuel trim swings

  1. #1

    Help with fuel trim swings

    hey guys. i seem to be at a loss in regards to fuel trim swings. it would seem that at times, hot engine or cold engine, trims across the board will swing positive or negative. if i data logged 4 sessions in a row on a hot engine, each time could vary.

    my fueling and timing is 99% to where i want it. is there an EGT or Catalyst table i need to modify? swings don't seem to follow air temp or coolant temperatures.

    from what i can tell, there are only maps 12451 fuel after start, 12452 fuel after start and 12405 catalyst heating. i do see map 11298 and 11301 but not really sure how to decipher. whichever map is jumping is is not tuned correctly for my setup and its causing swings of +12 or -12 until i've driven for longer than 15-30 minutes of which it cycles off and relies on standard tables.

    if no input from anyone, i'll begin trimming down 12451 as this it the map that pertains to my ECM. this map seems the most logical one to me. only concern is that even on a warm but not hot engine, fuel trim swings still do occur. this table ends at 45C which would include times when I would seem odd fuel trims
    Last edited by hachiroku; 12-02-2019 at 01:28 AM.

  2. #2
    another update...

    mapping is perfect with -3 fueling across the board as i've tuned for. after about 1 hour of driving, then fuel trims start going from -3 as i've tuned for to +3 across the board.

    is this a function built into the ECU for error and sensor checking? is anybody else experiencing this?

    drivability is the same, everything is running great. only difference is fuel correction swings from negative as i've tuned to positive after around 1 hour of steady driving.