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Thread: Why does this engine want to idle at 1500RPM

  1. #21
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    TroyZ06.ctz

    Here is the current tune file. Its not tuned just trying to get it to idle correctly. I sprayed the entire intake and throttle body with brake clean to see if I had any vacuum leaks but didn't find anything.

  2. #22
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    Quote Originally Posted by sparkinak View Post
    TroyZ06.ctz

    Here is the current tune file. Its not tuned just trying to get it to idle correctly. I sprayed the entire intake and throttle body with brake clean to see if I had any vacuum leaks but didn't find anything.
    That was a pretty short log. But I did notice your IAC steps went to 0 and it was still idling at 1500 rpm. The engine will not be able to idle down to your desired idle speed if the valve is all the way closed and still pulling in 18 grams/sec of air. I would try closing the throttle blade and see if that helps lower the idle down. Shoot for 60 steps at hot idle. Air seems to be coming from somewhere.

    Can you adjust idle with the DVT controls?
    00 Silverado Z71, LQ9 w/ LS3 heads, BTR cam, Whipple 2.9@8#, 4l80E

  3. #23
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    s10iac1.efi


    I knew I should have asked how long of a log I should have gotten. I have another one I took that I will post as well. If my IAC is going to 0 how would I adjust that? I thought that was B4401/B4402?

    As far as the throttle blade, I checked that the cable was seated properly and I checked the set screw which at this point I backed it completely of the blade linkage. Something that came to my mind just now is I wonder if my throttle cable is just tight enough it has opened that butterfly and that is why I am getting that tiny .4% TPS signal.

    DVT, I played around for a quick second to see if it would do anything. The only thing I got to work was doing the injectors on and off. I did not mess with it long enough to try throttle as my brain was confused on why it was idling so high.

    I'm also starting to wonder if there is something up with the IAC. Something like maybe the bore is wrong size or no deep enough etc. I see there is a difference between ls1 for 98/99 and the 00/02 models.
    Last edited by sparkinak; June 28th, 2016 at 06:44 PM.

  4. #24
    Joe (Moderator) joecar's Avatar
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    Does your throttle blade have a hole in it...?

  5. #25
    Joe (Moderator) joecar's Avatar
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    Did transmission die from low pressure...?

  6. #26
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    No hole in the blade, just a ls2 Holley 90mm tb out of the box.

    No tranny didnt die from low pressure? Did I miss or overlook something

    Sent from electronic life sucking device.

  7. #27
    Lifetime Member limited cv8r's Avatar
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    Your log had quite a few EGR codes. Is there any way it could be getting air through the EGR at idle?
    It's all good until it goes "Bang"

  8. #28
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    Quote Originally Posted by limited cv8r View Post
    Your log had quite a few EGR codes. Is there any way it could be getting air through the EGR at idle?
    No egr on this. I noticed that as well and will correcting the egr setting codes on next upload....

    Sent from electronic life sucking device.

  9. #29
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    Quote Originally Posted by sparkinak View Post
    ...

    No tranny didnt die from low pressure? Did I miss or overlook something

    ...
    What was the cause of the trans dying...?

  10. #30
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    Quote Originally Posted by LastCall View Post
    That was a pretty short log. But I did notice your IAC steps went to 0 and it was still idling at 1500 rpm. The engine will not be able to idle down to your desired idle speed if the valve is all the way closed and still pulling in 18 grams/sec of air... Air seems to be coming from somewhere.
    +1 I agree, air is coming in from somewhere.

    Are you sure EGR port in manifold is plugged...?

    Are you sure PCV is not pulling air in...?

    Post pic of engine bay showing PCV.

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