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Thread: GT500 Weird idle issue when clutch depressed

  1. #1

    GT500 Weird idle issue when clutch depressed

    I had this GT500 motor come in with a bad motor. Low holes. Rebuilt the motor and went to tune it when i found a weird issue i've never seen before. Its a 2013 gt500 with a kenne bell, return fuel system, stage 3 cams, DW 200lb injectors, etc. When i built my base tune got it running and dialing it in, i noticed when pressing the clutch the spark would drop negative and start surging really badly. I've done a few builds like this and have had a good base tune for these things. I played with a bunch of things to try to figure it out and nothing. Took a look at the tune that it came in on and they had this sucker running -12 degrees at idle. So i threw those settings into it and sure enough press the clutch and nothing changes. No way this can be right. If i try to run any regular idle timing in this thing, the second the clutch is pressed the timing drops to min and of course throttle body tries to react for it and surges bad. I've tried playing with min spark and such and if i raise it to let say 10 degrees, it'll go straight to 10 degrees and stay there when clutch is pressed. I looked at all source values and nothing changed with clutch pressed. Any ideas on this?

    Stock tune is one it came in with. My base tune is all over the place now from playing with it.2013 GT500 - Hussain - Stock tune.hpt2013 GT500 - Hussain - built motor final.hpt

  2. #2
    Potential Tuner
    Join Date
    Oct 2017
    Posts
    6
    Its completely normal based on the KB tunes to have the idle spark at -12. I was told this is what they found worked best to help stabilize the idle with the big T/B's. That's what I was told. I have found that sometimes depending on the mods I've gotten much smoother idle letting it drop to -14 to -16 at idle. I'm not sure why pushing the clutch in is giving you more issues unless there is too much end play and it is starting to drag the engine down when you push the clutch to the floor. But you mentioned with the spark at -12 it seemed just fine?

    Which KB in on there and which T/B?

  3. #3
    3.6L Monmouth with monoblade. Doesn't this superheat the exhaust? Still weird how the second i press the clutch the spark drops to negative even though commanding around 20 and idle goes crazy. Air flow tables are the same for P/N and Drive.

  4. #4
    Advanced Tuner
    Join Date
    Jul 2017
    Posts
    529
    Is it changing idle control source, when clutch is depressed?
    Mine would change sources when I pressed the clutch, but I've since tuned around that.

  5. #5
    it doesn't change that's what's throwing me for a loop. here is a log. You can tell when the clutch pedal is depressedSpark drop with clutch pedal.hpl howd you tune around it?

  6. #6
    Advanced Tuner
    Join Date
    Mar 2010
    Location
    New Orleans, LA
    Posts
    628
    if you don't want clutch specific functions then change TRLOAD the transmisission load switch from 2 to 0
    decipha @ EFIDynoTuning
    http://www.efidynotuning.com/