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Thread: Connect & cruise ls3 / rough idle

  1. #1
    Potential Tuner
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    Connect & cruise ls3 / rough idle

    I have a brand new out of the crate factory tune LS3 500hp / 6.2L with a T56 6 spd.
    Headers, cold air K&N for the 6.2L

    It will not idle smooth and is pulsing like it has a large cam. Runs great other than that and no DTCs. 24-09-19 12-50-38.hpl
    It is also slow starting / cranking before a sluggish start, not every time but most.

    I purchased the MVI3 HP Tuner and recorded the tune to post and see if anyone can point me in the right direction.
    A newby at using the HP tuner. I have been researching on what direction to take but any input would be helpful.

    I have 50 miles on it and I noticed that coming off the throttle it drops way down to approx. 4-500RPM almost then back up at target idle but still pulses.


    Thank you

  2. #2
    Senior Tuner
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    Nov 2017
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    Need to post the tune also.

  3. #3
    Senior Tuner
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    It looks like it just needs to be tuned. How the MAF is mounted completely changes the tune and that has to do with your swap.

    calibrating the MAF table, you could use fuel trims to do this.. would be step one
    Tuner at PCMofnc.com
    Email tuning!!!, Mail order, Dyno tuning, Performance Parts, Electric Fan Kits, 4l80e swap harnesses, 6l80 -> 4l80e conversion harnesses, Installs

  4. #4
    Senior Tuner TheMechanic's Avatar
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    Had the exact same thing happen a couple years ago. Post your tune and I can do a compare and see if there is anything odd. I remember changing some BRAF and reducing the overspeed and underspeed timing. It's on my server at home so I won't be able to get it until tomorrow.

  5. #5
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    I do appreciate the feed back and I thought it might have something to do with the MAF location and swap as well. This is the log of the current tune that came with the C&C package.
    https://1drv.ms/u/c/655bf7a5fffafd45...U33Sg?e=Id8Prm

  6. #6
    Senior Tuner
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    Most people aren’t going to mess with links for tunes/logs. Need to do an attachment to a post.