aklim

And gaskets. Don't reuse them or condoms either

temcgregor

I have High idle 1100 rpm or so. What is the IAC

MatthewMiller

Idle Air Controller. It's a small stepper motor that controls the idle air passage. The computer uses it to control idle speed by varying the idle air opening. You'll find it screwed to the bottom side of the throttle body.

temcgregor

Doesn't 1000+ seem a little high?

MatthewMiller

It's about right for cold startup idle. But for a stock engine that's already warmed up, yes that is high. I don't know which engine you have, but as a reference, on a stock LT4 the computer targets 1050rpm at cold startup and it tapers down to 700rpm when warmed up. And that engine probably has the most radical (but not very) cam of any C4. So an LT1 or L98 might even target 650 or 600.

temcgregor

I have the stock LT1

MatthewMiller

I don't have the calibrations for that engine, but it is a safe bet that it should idle somewhere within 600-700rpm when warmed up and in Neutral gear.

DGXR

I think high idle can be caused by a vacuum leak. But wouldn't the IAC valve try to adjust for a high idle, no matter the cause?

aklim

It would until you run out of adjustment
See what the scanner says

KyleF

This is why it is important to have a scanner, not just a code reader, when diagnosing problems.