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Thread: maf adjusting not changing afr

  1. #1
    Tuner in Training SDCE's Avatar
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    maf adjusting not changing afr

    working on a na 2000 5.3 transplant and cant seem to get the afr to change either with maf adjustments or sd tuning with the maf failed .
    also will not go into cl .but one of the o2s always reads 450 mv.
    another weard thing is the knock retard pulls max allowed timing no matter what total timing i pick .
    limp mode maybe ?
    corrupt ecm ?

  2. #2
    Tuning Addict 5FDP's Avatar
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    Are you running a wideband?

    Are you talking commanded AFR or the AFR you see on a wideband?

    It won't go into closed loop if one of the o2 sensors is not working, 450mv is a dead give away that it has no power to the sensor.

    Post tune and logs with any information on the swap. What parts are you using, is it all stock or is stuff aftermarket?
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
    Tuner in Training SDCE's Avatar
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    I am using the wide band from my dyno to see the actual afr .For example i command 12.5 scan tool indicates 12.5 commanded at wot, actual afr is 13.2
    i cant make it change no mater what maf values or ve values i use .At idle actual afr 12.5 commanded 14.68 I cut maf lb /hour in half ,still nets 12.5 afr.
    All stock but cam and wire harness from unknown origin .
    Hope this helps.
    Attached Files Attached Files

  4. #4
    Tuning Addict 5FDP's Avatar
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    Okay, a couple things aren't lining up here. You have the dynamic airflow set to take over at 500rpm yet the MAF fail high freq. is set at 1,400hz. If you are trying to tune the MAF curve and adjust fueling that still needs to a much high number like factory at 13,500 so it can use the MAF correctly.

    Then when you tune SD you need to set the MAF fail high to 0hz and the 3 MAF dtc's to fail on first error to use SD. You can also set the dynamic airflow to a much higher number if you wish.

    I also see that the injectors are larger than the 25lb/hr that came factory, is that right?
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  5. #5
    Tuner in Training dgann's Avatar
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    I am currently working on tuning 02 Silverado ls3/4l80 conversion and I also had a problem with an o2 sensoer reading a steady 450mv. After further investigation, i had o2 sensor plugged into the wrong connector

  6. #6
    Tuner in Training SDCE's Avatar
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    Thank you, i totaly missed the 1,400 my brain told me it was 14,000
    I also went to the tune i was using to tune the sd and one of the maf dtc was previously set to no report .as far as injectors have no idea but at idle 7 ms duty if i remember .
    A FRESH SET OF EYES ALWAYS HELPFUL !

  7. #7
    Tuning Addict 5FDP's Avatar
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    I'd double check what injector size they are, not having the right size in there could throw off readings.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.