I have been having a high idle issue with my 93 camaro LT1. It is racing in P and all gears. At first glance it appears to be a vacuum leak. I checked my IAC and it starts at its default reading at about 130 or so and then quickly shoots down to 0. I have checked over the car very well for vacuum leaks and other misc. things. Let me know if what I did makes sense....

I started the car and let it get to operating temp and warm up. Obviously my IAC counts went down to 0. I then unplugged my IAC with the car running so in theory the PCM would not control it and it would stay fully closed (allowing no air bypass). Then I removed the throttle body and IAC assembly so that I could see exactly what position the pintle was in. If the IAC is in the position at 0 counts and allowing no air bypass, then the pintle should be fully seated against...it's seat...? When I took the IAC assembly off the throttle body, I noticed that it was only about half way to it's seated position. So if the IAC is stuck, and allowing excessive air bypass (vacuum leak) obviously the PCM is going to attempt to fully close the IAC. Either way I am replacing the IAC tomorrow but does that make sense in regards to how I am determining this high idle problem.

Also, I unscrewed the IAC pintle all the way so when I screwed the IAC back into the housing, the pintle was fully seat. I definatly broke the IAC but I am trying to prove a point that if the pintle is fully seated, the car will not run unless I give it gas....And that is exactly what happened.

Yes - no - maybe

 

Makes sense. Shoebox has a procedure for checking the IAC motor resistance. Did you try that?

http://shbox.com/1/iac2.jpg

 

no - did not do res. check - i ended up getting a new IAC anyway - i had to readjust my idle set screw since i messed with it previously - but all seems good to go regarding idle control - now if i could just get my $5k trans to function properly maybe i could drive the car using more than 1/2 throttle - but that's another story for another thread

THANKS!

 

Did you use Shoebox's IAC reset procedure?

http://shbox.com/1/4th_gen_tech2.html#iac_reset

 

i did that procedure and then cruised it at 40 mph also - i saw both procedures - either way - it seems pretty stable now - i wouldnt mind seeing my closed loop IAC counts a bit lower - but they are varying between 39 and 50 so I am ok with that for now - ....i'm having a problem with my TCC lock up also - my trans guy at Level 10 Performance in New Jersey redid the trans 2 years ago and it has never been the same since.....now he rigged up something in the valve body and is locking up my TCC in 4th gear at all times and 50mph in 3rd but the car is hunting and bogging and stumbling all over the place and lacks power at certain RPM's - so among that problem, he should also adjust my TV cable at the throttle body but either way - that's another story