When I drive at operating temperature the IAC counts are at 30 at idle after driving 30 minutes.
If I drive more than 30 minutes they start to go down....
Example, after 1 hour of driving, the IAC count is 0 at idle. I have driven car with vacuum gage hooked up and vacuum is fine.
To sum it up, seems like the more I drive it at operating temperature the lower the IAC counts get.
Any ideas ? do I need to adjust the throttle stop screw ?
The problem is with my Z28

 

A cold engine idles higher and requires more air to idle at the same RPM.

However an hour of runtime seems excessive to me for it to fully heat up, and it should never get to 0. Most agree that 30-40 counts at idle fully warm is a good point. Yes you can use the throttle stop screw for that, it wont take much. BUT i think thats only going to be a cover up for a problem elsewhere that hasnt reared its full head yet.

 

You should not have to adjust the throttle stop on a stock car. There is something that is causing the counts to go down (a vacuum leak can do it).

 

we have an adjustable throttle stop screw on our cars?

 

Yes, but it wont effect the idle at all because the IAC should automatically compensate.

However with cam/head/built motors, the IAC isnt fast enough or big enough to keep up with the motor, so you can crack the blades a tad to allow direct airflow into the intake, instead of through the IAC ports.

Its top drivers side of TB. To set it you need a torx bit. Entry is from firewall torwards radiator (you can see the tail end of screw holding open the TB linkage moon shaped piece where your throttle cable attaches under the black plastic.