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Thread: is my ecm taking a crap?

  1. #1
    Tuner Onomoto's Avatar
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    is my ecm taking a crap?

    So short and sweet i had a couple of issues this past week. Found a faulty maf that was giving me grief along with a bad coil pack.
    But i cant figure out why its doing what is is now. It started after a weekend racing and got worse. discovered i cooked the maf because i left the key in the on position to use the scanner to run the fans between runs because the settings wont let me do it with the key off. corrected that now it randomly drops spark rpms shoot up on the scanner but the car actully wants to die. i am feeling that the ecm is on its last leg and starting to flake out. yes i know i have negative timing. wanted to see if i could do a pop pop pow, tune
    2001 monte carlo swapped l67 on e85
    XP cam
    gen5 m90
    speed daddy headers 3 inch exhaust
    3.5-3.2 pully

  2. #2
    Tuner Onomoto's Avatar
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    took a longer log file. most of the time it was idling out of gear. i noticed that the ecm is commanding 15.7 afr and going into open and closed loop.
    Attached Files Attached Files
    2001 monte carlo swapped l67 on e85
    XP cam
    gen5 m90
    speed daddy headers 3 inch exhaust
    3.5-3.2 pully

  3. #3
    Tuner Onomoto's Avatar
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    Noticed the 02 sensor is staying rich a lot. Then the open loop follows.
    2001 monte carlo swapped l67 on e85
    XP cam
    gen5 m90
    speed daddy headers 3 inch exhaust
    3.5-3.2 pully

  4. #4
    Tuning Addict 5FDP's Avatar
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    Looks like it's cycling through a cat test that HP Tuners can't disable if I had to guess at it. I know the much older DHP Tuner can disable that but you'd need own it or know someone with one to disable it. This problem happens on the 2001+ computer because of changes in emissions. The older 1997-2000 don't have the cat test.

    There might be a work around with installing the rear o2 sensor in the exhaust is spacing the sensor out enough to not trip a P0420 code for under performing cat.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

  5. #5
    Tuner Onomoto's Avatar
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    5fpd. That might be true but I have never seen it before on past log files. Plus the way the rpms shoot up on the log is questionable because when it does that the engine mis,s. Along with other problems I will do a hard pull and right when it goes to shift on the 1-2 its like the ignition is switched off and the engine dies. It doesn't always start right back up. I pulled the plugs and they don't look to hateful taking the injectors tomorrow to have them tested.
    2001 monte carlo swapped l67 on e85
    XP cam
    gen5 m90
    speed daddy headers 3 inch exhaust
    3.5-3.2 pully

  6. #6
    Advanced Tuner ZeroBoostBuick's Avatar
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    I've seen them command higher than 14.7 for several seconds right after start up when the engine is already fully warmed up.

  7. #7
    Tuner Onomoto's Avatar
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    I have a concern about how the rpms spike up with no throttle input.
    2001 monte carlo swapped l67 on e85
    XP cam
    gen5 m90
    speed daddy headers 3 inch exhaust
    3.5-3.2 pully

  8. #8
    Tuner Onomoto's Avatar
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    Had the injectors flow tested and cleaned. Replaced plugs and 02 sensor. Runs like a champ now
    2001 monte carlo swapped l67 on e85
    XP cam
    gen5 m90
    speed daddy headers 3 inch exhaust
    3.5-3.2 pully

  9. #9
    Advanced Tuner ZeroBoostBuick's Avatar
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    Damn, that's good to hear.