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Thread: Gm performed crate ls3. with a bad tune

  1. #1
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    Gm performed crate ls3. with a bad tune

    So this is the story i got. gm motor and stand alone harness out of the box installed into a jag. installer put a 3" intake tube on it. and sent it out for tuning. the tuning guy said the intake was to small and did some sort of tune on the engine. i think he was trying to compensate for the intake. it runs bad mostly after it warms up. i have a new 4" intake to go on it. this is total new to me. first time trying this. i have been a gm mechanic for 15 years. i will attach my tune file.

    Jag.basetune.hpt

  2. #2
    How "bad" does it run after warm up? Too rich? Won't accelerate? Won't idle? What, exactly, is the problem? This will narrow down where to look inside your tune but an HP Tuners log file recorded during a drive would be even better.

    Rick
    1970 Chevrolet El Camino LM7 5.3 liter mill and a 4L60E transmission.

  3. #3
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    Ok great. I will do that.

  4. #4
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    hello looks like it is subtracting fuel to much. so new to this not sure were to start. i will added the tune and the road test. feels like a missfire on acceleration but is not logging missfires.
    Jag.test1.hpt20-05-24 08-09-30.hpl

  5. #5
    Hello,

    I'm certainly no expert here but it does not look all that bad to me. I don't see any knock reduction - this is a good thing. Your Long Term Fuel Trims settled out to -10 after being quite high at the beginning but that -10 is not all that bad. I've seen mine worse at -25 before changing out my intake and air filter oddness - something about causing chaotic air at the MAF.

    Your engine is not running hot. No cylinder misfires. Timing looks as good as mine under similar conditions. It is in Closed Loop. Your O2 sensors seem to be responding well. Fuel pressure is good at all times. PCM Control voltage is good.

    I guess the only minor concern for me would be a slightly too fast of an idle RPM at 850. I like 650 RPM but hey, that's just me. Edit: You might bump up your stall saver RPM a little - it got down to about 450 RPM at one point.

    You don't mention your transmission at all. Is it slipping? Does it shift correctly?

    Rick
    Last edited by B52bombardier1; 05-24-2020 at 01:40 PM.
    1970 Chevrolet El Camino LM7 5.3 liter mill and a 4L60E transmission.

  6. #6
    Advanced Tuner jsllc's Avatar
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    Is based on your log. You went WOT and it took 4 secs to get to 40mph from 10. Is that correct? The MAF and VVE if gen4 need adjustment as they are off by well over 10%
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm