Ok, I'm at wits end here.

Engine idle runs high. On cold starts, it gradually climbs from around 1k, up to 3k if I let it. On warm starts, idle stays high, and won't come down. "Sometimes". A lot of work has been done to the car recently. As far as things done that relate to this idle issue, there's NO vacuum leaks, CTS is new and circuit is good, timing is correctly set at 10 degrees, throttle body gaskets are good, IAC is clean, so is throttle body. TB has no play, valve closes and opens like it should, otherwise perfect condition.

I have done a huge number of tests, and troubleshooting this, but I'm stuck at either IAC is malfunctioning, or ECM is going bad. I could use any advice you can throw at me, I've prolly already done it, but I don't care. I need to get this problem solved, and need as many heads on it as I can.

BTW, it's the car under my avatar....88 sport coupe, 2.8 v6

 

This is my IAC valve s closed as the car will make it. I did this by jumping a and b in the diagnostic port, and waiting 30 seconds, then unplugging it. Is this right? Or should it retract all the way in? Also, I cannot get the shaft to move in or out. I read a post saying it should be movable.

 

Does your engine have a throttle positioning sensor? I replaced mine cause it had similar problems, and now it runs normal.

 

Yes, I have a TPS. It's set as close to spec as I can get it. I might also mention that the car is running really rich. Is there any way I'm having issues because of my altitude? Is there a chance the computer isn't compensating enough? Also, I unplugged the MAF, and the car wouldn't stay running, plugged it back in, it's good again.

 

going through the same thing right now cold start on 1k and 1500 rpms on my warm start ups