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Thread: E67 crate LS3 idle issues

  1. #1
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    E67 crate LS3 idle issues

    I have here a LS3 "hotcam" crate engine in '60 Impala. It has been running fine for years with the tune that was with the car originally. Now the intake air duct has been modified longer to take air from colder area of the engine bay and I thought the idle problems were due to the MAF being relocated and not dialed in.

    I started with dialing in the MAF and noticed than "conveniently" the MAF was already enabled from idle rpm. The dialing in process didn't help me at all. It still has very poor idle and it stalls every time I come to a stop. Then I looked into other idle stuff and noticed many things differing from "VIN-coded LS3". First of all this car thinks it's a manual but it has 4L65 tranny in it which is controlled by a separate box. It seems that everything I touch takes the idle completely away. It just doesn't seem to handle anything below 1000 rpm.

    I took off MAF connector and spent few hours dialing in the VVE (there was 30 % fuel trims all over the VVE). I got it sorted or a leap closer to what I wished for but the idle problem is still there.

    I tried at least 10 different approaches to timing and idle timing and every time I tried a less agressive timing correction, it doesn't want to run below 1000 rpm at all.

    Driver side exhaust sounds like it's leaking right from the seal which is next to the O2 sensor, could that mess this up so badly? I tried to force to open loop on idle too but it didn't do much good.

    Could someone share LS3 hotcam E67 file so I could see where the differences are? I enclose here the original tune and a short run with it. Then there is one tune without mAF and longer run with that.
    Attached Files Attached Files

  2. #2
    drive by wire? prob not going to be able to rely on the MAF in the low rpms if the cam is lopey. go open loop and log stuff like commanded throttle, spark, spark adaptives, and of course stft if you don't have a wideband. why not put the intake back where it was? was it running fine before?

  3. #3
    running closed loop with an exhaust leak before your O2 can cause probs

  4. #4
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    Now the exhaust leak is fixed and with high hopes I started the car with GMPP tune. It idles at least when cold. Then I changed the tune to fix the VVE table which seemed to be quite off from GMPP. It doesn't idle anymore at all.

    I noticed that the fresh air tube from passenger side valve cover doesn't go where it should (between MAF and T/B) and it takes all fresh air from engine bay. This must be fixed but I think this wouldn't affect since the tune doesn't count MAF now so it shouldn't interfere with airmass.

    I enclose here short log where I run the car and slowly ease on the throttle. When the rpm go below 1000, it stalls immediately. I try to start it and not touch the throttle but it doesn't run. With my feet on the throttle it starts again but dies when I lift off.

    What is that "desired throttle position"? It's different than TPS all the time.

  5. #5
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    This EZ-TCU causes also some headache since the ECM doesn't know anything about transmission status and can't control the idle on neutral vs gear. I'm thinking that if I look for a GM transmission controller and re-flash the ECM to something that had the automatic transmission, I could tune that at once. Today I noticed that this EZ-TCU tune had TCC lock at some 150 mph and when I put in to 40 mph it locked but didn't release even if I stopped. Either the TCU is doing something wrong or the transmission has issues. I had to tune it back to high mph not to activate it again.

    From what car I should look for the transmission controller to pair with this E67 ECM? Then I will pay 2 credits for another tune and call it a day?

  6. #6
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    I have read a lot of E67 pairing with T42 during past few nights and I have realized I might be well over my head on this.

    So the car has LS3 paired with 4L65. There is an aftermarket TCU controlling the transmission and I?m hoping to get the whole combo to be tuned at once and to communicate properly with eachother.

    What choices do I have? From what I?ve read, E67/T42 will require a lot of work at least with 4L80E but is it the same with 4L65E?

    I even thought of swapping the reluctor wheel from 58x to 24x to make it simple but tearing apart a functional engine doesn?t seem wise. Would the next best way to change the ECM to E38? Or is there perfect match for E67/T42?

  7. #7
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    2007-up Trailblazer used E67+T42, 4L60/65/70 are functionally interchangeable.

  8. #8
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    Thanks! So the hard part would come only if I had 4L80E?

  9. #9
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    No that's not hard either. Lots of Trailblazer SS's get swapped to 80Es, it just takes some creative wiring or a pre-made relay harness. Still using the original TCM OS just with adjustments in the tune.