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Thread: IAC closes to 0 on cold start sometimes but not every time.

  1. #1

    IAC closes to 0 on cold start sometimes but not every time.

    1999 Camaro Z28 m6. About 5 or 6 times now on the initial cold start the iac goes to 0 and is commanded to 0. As you can imagine, the car has not hope of running after the initial fire if the iac is on 0....especially on a cold morning.

    Yesterday before leaving the shop the car was completely cold and it fired up perfectly with the iac on just over 200 counts and trimming down as it should as the car warmed.

    This morning, the car went right back to 0 with key on. When turning the key off and the log still rolling you can see the iac open back up. Key back on it goes back to 0. I did this quite a few times in the log im attaching so that you can see. Every time the iac goes to 0 it is because I have keyed back on.

    Any thoughts? This problem is another new one on me....and the fact that it only does it sometimes is very strange and the fact that the iac works as commanded makes it even stranger. What in the programming would tell the iac to go to 0 with the key on and a cold start?
    Attached Files Attached Files

  2. #2
    Here is a log taken right after the first log posted. On this log I actually gave the car throttle to make it run. The IAC stayed on 0 for the first 50 seconds or so and then magically started to work like it should.

  3. #3
    Senior Tuner
    Join Date
    Feb 2009
    Posts
    1,931
    Run the russ k idle airflow config. I am wondering if it has something to do with your commanded airflow exceding the maximum. You do have it set quite high and the trims are pulling large amounts of air.

  4. #4
    Senior Tuner edcmat-l1's Avatar
    Join Date
    Aug 2006
    Location
    5BA8
    Posts
    3,051
    Too much total idle airflow. Give this one a try.

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