454 Idle Help

Alright, I recognize this is the Fiero forums, not big-ass truck forums, but still, they're both GMs, and I'm hoping one of the TBI guys might be able to help.

My 454 was idling stupid high (Around 2000RPM) before I noticed the IAC had been disconnected. Since re-connecting it, the truck has settled down to about 1500RPM, which is still too high to even put it in to AirCare. I've checked for vacuum leaks, and there arn't any. I've also tried manually forcing the idle set screw lower (Which is a challenge in and of itself) and even with the throttle blades closed completely, it still wont go down below 1500RPM. It had a code for low throttle position voltage before, but that's gone now, for what it's worth, and no new codes have taken it's place.

Any ideas on what's causing it to idle so outrageously high?

Sorry, should've mentioned, I already checked for vacuum leaks (They were quite common on the TBI 454), there are none.

I'm beginning to suspect it is the IAC. Haven't tried jumping it yet, but I know when I helped "plug" the IAC (Wrapped electrical tape around the tapered section of the valve, closing it off more), the idle settled right down. I actually have the EGR pulled at the moment, however, so it wont be that either.

I'm thinking you're spot on with the IAC though. I'll try jumping it tomorrow.

Well brother, I may have missed a vacuum leak, but in the mean time, the IAC was the way to go. It doesn't adjust back all the way, so there's a constant, large supply of air rushing past. I'm going to replace both the IAC and it's connector (The connector ain't looking so hot...) to be safe. In the mean time, my electrical tape solution seems to be holding up just fine.

Thanks for your help, Doc.