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Thread: underboost acts like ignition is shut off till I let off thottle then repeats

  1. #1
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    underboost acts like ignition is shut off till I let off thottle then repeats

    Car cuts out under wot and will die if I do not let off throttle. If I do let off throttle will regain, but does it again if I go wot. I have tried a new crank sensor and relearn I have also tried multiple tunes. Same problem persist. What do I need to do. Thanks in advance.
    5.3
    80lb sd
    gt45 12psi (only gets to 7)
    sometimes will hit 4200 rpm
    Attached Files Attached Files

  2. #2
    Tuning Addict 5FDP's Avatar
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    Cylinder volume is wrong for a 5.3, set all 3 MAF dtc's to fail on first error for speed density tuning. I know matt doesn't do that with many of his SD tunes you find on sloppy but you do want them on first error.

    You should log the right MAP sensor channel, current one stops at 105kpa. Log commanded AFR too, fueling is going way rich once you hit boost?

    Are you running a 3 bar MAP too? Are you running o2 sensors are is it totally open loop with no o2 sensors?
    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
    What is your plug gap at?

  4. #4
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    Didn't check maf error on this one. Will change my channels. 2 bar map both o2 sensors. I have tried both loop setups along with multiple tunes. I really feal it's an input. Which is why i tried a crank sensor. But i am lost. On a side note if not under a load will rev to limit without issue.

  5. #5
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    Also car has solid engine mounts. Should rule out wiring harness being pulled.

  6. #6
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    Plug gap .28

  7. #7
    Tuning Addict 5FDP's Avatar
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    You need to change the linear and offset settings for the 2 bar map, it has settings for a 3 bar map currently.
    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.

  8. #8
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    Torque management is still enabled.

  9. #9
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    Made all the above changes recommended. Still acts like you shut the ignition switch off till you release the throttle. Could a bad map sensor or cam sensor cause this issue. It's only under a load it happens. When doing a crank relearn it revved no problem. I'm desperate for an answer. Just want to enjoy this build.

  10. #10
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    Happens between2500 and 4000 but happens everytime under load

  11. #11
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    cam position sensor fixed it