First off, I've got an '87 IROC w/ 305 TPI.

It's wierd, but sometimes my car just WON'T idle. Usually, if I start it and let it idle, it does just fine....

However, sometimes after driving it for a while, I'll come to a stop light and she'll idle at 450rpm or just plain die.

Sometimes it just idles and others it just doesn't, there's no pattern.

My idler screw isn't moving as far as I can tell.

Any ideas why my IROC-Z doesn't wanna idle sometimes?

 

Does the engine being hot or cold effect it?

 

do you have a hypertech chip in your car?
I did and as soon as replaced it with the stock chip the idle problem left , even ran a little smoother and stronger

 

It does seem to only do it when the engine is warm.

No, I don't have a chip, its all stock.

 

My car was doing the same thing, I cleaned and replaced the IAC and the housing; but if was working after that. Seems the counts would get messed up with the heat.

 

check your timing or your TPS, and like Maroon saide you IAC coudl be shot, also does it back fire when you give it gas off and idle? could be timing then or a bad MAF

 

I got the same problem with my 91' Formula. It seems to have problems idleing but only when i start it up. Can anyone point out exactly where the ideler screw is and what i can do to change that idler problem? It never stalls out just runs really rough and idles around 450-500rpm. I was also wonder what the IAC was and what i can do to clean it out. Thanks again.
Kyle

 

Look at the throttle body on the drivers side. You will see where the control cables (throttle, kickdown, and shift cables) attach to the side of it. Look at the throttle cable, it is attached to a metal bracket, technically they all are, but it has a screw holding it from coming back and touching the tb after you release the throttle.

The screw can usually be seen looking on the drivers side of the TB, and looking towards the front of the car. It might have a saftey cap over it, you will need a punch and a T20 torx bit to move it.

The IAC (idle air control valve) is really a motor. The computer doesn't move the throttle blades to control the idle of the vehicle. It uses a motor with a pintle tip to open a close a smaller hole under neath the tb blades. This is located in the passanger side, underneath the tb. It has a square four wire plug. To adjust it, go here and read how to do it:

https://www.thirdgen.org/newdesign/tech/tpimod2.shtml

Also, adjust your TPS sensor first, then go on to mess with these other two.