89 iroc 305 tpi 5 speed... i have had this idle problem for quite some time now, and it just is anoying... the throttle sticks open about 1800-2000 rpm i can make it drop down by pushing the throttle closed or floor the peddle and let it back out within a 1/4 second. when the engine isnt running, the throttle will close completely with ease i posted the question before and none to the responses really helped, so now i have tried adjusting the aic and and tps, but after i unplug the aic connector i cant get the car to idle any lower than 650 or it will die, the tech article says it needs to idle at 450 for it to be correct, but i cant get it to idle that low, it will die, anyone know why? or am i doing this wrong, could it be a vacume leak, when i let the car idle for about a minute, and i hit the throttle really quick, i get a little puff of white smoke off the back of the engine.

 

1. is the car at normal operating temperature.
2. was pin "A" & "B" of the ALDL jumpered for 30 seconds with the key in the "ON" position to reset the IAC valve before it was disconnected and the jumper removed.
3. was the gear shifter in drive when you set the idle speed to 450.

 

Sounds like its time for a new throttle body or have the present one bushed if it can be. That should solve your problems. The throttle hanging is due to the engine vacuum pulling the shaft and butterflies back and because the wear is off-center, the butterflies hang on the bore walls and the throttle sticks open.

 

yea i had the a and b connected for 30 secs, and it was at normal operating tempature, im pretty sure its is caused by the vacume holding it open, but im still concerned about not being able to set the aic what kind of a problem would cause it to die at 600 rpm, i have that little puff of smoke from the back of my block that comes out when i rev the engine would this keep it from idleing that low? when i do get it to idle when it in normal operation, it jumps from 750-1000 rpm constantly.

 

You cant really set or adjust the IAC as its fully under the ecms control and the ecm handles resets automatically. The whole 'A + B' thing is to force the ecm into field service mode so itll seat the IAC. You can then disconnect teh IAC, pull all items out of the ALDL and start the vehicle. From there you then mess with the throttle stop screw to get the base idle speed where you want it. After you reconnect the IAC, the next time you shut the motor off after the restart, the IAC will be reset and parked. From there, see how it works. About it dying at 600 rpms, is your tach correct? The rpms could be lower without you knowing about it.

 

i was using an inductive engine analizer unit, and it is pretty accurate. so what you are trying to say is i should set my base idle with the iac connecter disconnected? i thought i was supposed to set it to 450 rpm and then when i plugged it back in, it would self adjust it to the correct idle speed.

 

You want the IAC to be unplugged after its been seated and teh car to be running in normal operation (ie nothing in the aldl). This way, there is no interfierence from the computer to adjust the idle or alter the way the motor would normally run.