I'm pulling code P0507: Idle Speed Control Engine Speed High Fault.
I took my car in to chevy and they said they couldn't troulbleshoot w/ an aftermarket Tb on it, but they told me my iac count was at zero.I know alot of people have this throttle body and was wondering if you ever succeeded
in getting this thing to run right.I've read alot of things on this board about it and can't seem to come up with any exact solutions. Thanks, Mike

 

the most common fix is to readjust the throttle stop. sounds like you need to close it. The second most common fix for an aftermarket TB is switch back to stock I did after fighting with a hollet TB fo 3 months. Ported stocker that is.

 

How do I know if the throttle stop is adjusted correctly?I would really like to keep my current tb .It sounds like you have alot of experience in the feild, any other advice.

 

Is your engine idling where it normally does, or is it idling faster than normal?

If your IAC is at zero, what's happening is it's trying to control the idle of the engine and closed all the way. Basically what's going on is there's too much air being let into the motor at idle, either via the TB or through some sort of vaccuum leak. Odds are it's the TB.

You need to close the TB blades via the throttle stop until the IAC starts to react to control the idle of the car. Make small adjustments, turn off the car, give it a couple of seconds, restart it and check to see where you're at. This is all a non-factor if you don't have some sort of scanner though, as you'll just be guessing where the IAC counts are.

Also, it's very common with an aftermarket TB to need to adjust your TPS too.