High Idle issues with IAC connected.
Thread Starter
Joined: Feb 2005
Posts: 716
Likes: 2
From: Minneapolis MN
High Idle issues with IAC connected. Engine: 2004 LS1 out of a GTO.
Changes done: LS2 intake, LS2 injectors, 90 mm TB, Stock 2002 LS1 tune.
Issue: With the IAC connected, the car will idle at 2000 rpm or higher all the time. If I disconnect the IAC and restart the car, it will idle fine at 800 - 900 rpm.
Things I have done:
checked for vacuum leaks. none I can find.
Adjusted the TB by closing it. No change
Reset the TPS several times. No change.
Checked for vacuum leaks again. None that I can find.
I found two other people that have the same issue. Neither one of them has figured it out and have been running with the IAC disconnected.
http://www.ls1.com/forums/showthread.php?t=110370
http://www.hptuners.com/forum/showthread.php?p=247582
Any help is welcome.
Changes done: LS2 intake, LS2 injectors, 90 mm TB, Stock 2002 LS1 tune.
Issue: With the IAC connected, the car will idle at 2000 rpm or higher all the time. If I disconnect the IAC and restart the car, it will idle fine at 800 - 900 rpm.
Things I have done:
checked for vacuum leaks. none I can find.
Adjusted the TB by closing it. No change
Reset the TPS several times. No change.
Checked for vacuum leaks again. None that I can find.
I found two other people that have the same issue. Neither one of them has figured it out and have been running with the IAC disconnected.
http://www.ls1.com/forums/showthread.php?t=110370
http://www.hptuners.com/forum/showthread.php?p=247582
Any help is welcome.
Last edited by Schitzo; Mar 17, 2011 at 10:14 AM.
Thread Starter
Joined: Feb 2005
Posts: 716
Likes: 2
From: Minneapolis MN
alright guys help me figure this one out. Here is a log. The first few seconds are of the car idling with the IAC disconnected. You can see the IAC steps are high
the tune is posted above
the tune is posted above
Curious if anyone finds anything out on this. I can't for the life of me solve this on my car either. Swapped the IAC to 2x known good ones, no change. Stock tune, no change. Toned out the wires, verified they're all good... I'd love to have my IAC hooked up, as the car is a bit "cold natured" on initial startup.
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Did you have the IAC connected during the end of the log.
Reason I ask is because from what I looked at in the log it was idleing right at 800-900 like you say. Even at the very end of the log.
So maybe the high IAC count is due to it being disconnected and not being able to reach the desired?
Reason I ask is because from what I looked at in the log it was idleing right at 800-900 like you say. Even at the very end of the log.
So maybe the high IAC count is due to it being disconnected and not being able to reach the desired?
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I've experienced a similar issue in the past...I suggest checking the operation of the TPS. Make sure the voltage output and throttle opening percentage are steady from throttle closed to full open. Usually, the TPS wears out in the closed to just off idle position area and will show up as erratic voltage output or throttle opening percentages. To troubleshoot, I used HP Tuners to view the voltage and throttle percentage as I moved the throttle from open to close. In my case, the TPS was bad.
Thread Starter
Joined: Feb 2005
Posts: 716
Likes: 2
From: Minneapolis MN
I've experienced a similar issue in the past...I suggest checking the operation of the TPS. Make sure the voltage output and throttle opening percentage are steady from throttle closed to full open. Usually, the TPS wears out in the closed to just off idle position area and will show up as erratic voltage output or throttle opening percentages. To troubleshoot, I used HP Tuners to view the voltage and throttle percentage as I moved the throttle from open to close. In my case, the TPS was bad.
Thank you very much. My high idle issue is fixed thanks to a new TPS.
Decided just to buy a new one before logging anything. Installed the new sensor started the car and it revved up to 2000 as usual. So I thought I was out of luck again. However I thought maybe I should reset the TPS. Sure enough after resetting the TPS the car now idles fines.
Red you rock!!
