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Thread: Supercharged LSX hesitation and idle issue

  1. #1
    Tuner in Training
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    Supercharged LSX hesitation and idle issue

    Hello everyone,

    I recently bought a 2004 C5 Corvette with a LSX 376 and a Magnanuson TVS2300 SC. The previous owner had passed away and not much is known about it. I did a full tune up on it as it had been sitting for over a year - changed all fluids, filters, spark plugs (.40 gap), wires and replaced generic ebay coils with some MSD coils.

    The issue I am having is a hesitation and stumbling around 1700rpm to 2400rpm. After that it drives just fine. Also the idle would randomly stay at 1500rpm for a little while then slowly come back down..

    I can do a datalog (just got my hptuner) and post it or post a dump of the whole tune. Still playing around with the hptuner without doing anything dangerous or risky as a newbie lol.
    Last edited by fastloud; 05-22-2021 at 02:22 AM.

  2. #2
    Senior Tuner Lakegoat's Avatar
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    Gap should be approx .025 for the plugs. What plugs? If you can, post the tune and a log.
    2000 Camaro SS 2015 L83 port injected, Whipple 3.0, 4L80E, 8.8 Ford
    2013 Silverado 5.3, 6L80k 8.8

  3. #3
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    Agree with the gap being closer to 0.25 or 0.028; and copper tipped plugs will be more forgiving than iridium.

    If I had to make a wild guess, you're too rich in the low load ranges, and the high idle is probably from a combination of too much minimum airflow, timing and fuel. But without data logs, it's naturally a completely wild-ass guess!

  4. #4
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    Hmmm maybe that's why it felt like I lost some power? Ok I will do a datalog soon and post, perhaps a dump of the whole tune. Thanks guys!

  5. #5
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    Quote Originally Posted by Random84 View Post
    Agree with the gap being closer to 0.25 or 0.028; and copper tipped plugs will be more forgiving than iridium.

    If I had to make a wild guess, you're too rich in the low load ranges, and the high idle is probably from a combination of too much minimum airflow, timing and fuel. But without data logs, it's naturally a completely wild-ass guess!
    Not sure if this would help, but here is a complete dump of the entire tune. I will take it out tomorrow or Sunday and do a datalog as well.

    BTW, I don't think I mentioned it but the car also uses a Boost-a-pump with the fuel pump.
    Attached Files Attached Files

  6. #6
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    Quote Originally Posted by Lakegoat View Post
    Gap should be approx .025 for the plugs. What plugs? If you can, post the tune and a log.
    I got a chance to take her out this Sunday and do a few logs. This is the first one from when I backed out of the driveway and got on the highway. Did a hard pull as well. I am using AC Delco 41-104 Iridium plugs currently gapped to .035
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