IAC problem

[Ger-Fire-Form-93]

Hi everyone,
long time since my last problem.

Ok, after replacing the old opti for a brand new ac delco and a new set of MSD wires.
The car start very strong,two minutes later begins a little high rpm (1000-1500) but an any moment it goes at very lows rpm, sometimes it almost dies.
I got no codes on my scanner, but i notice that IAC valve has not movements , just still 16, no matter if I push the pedal to the floor....just still 16.
I know the IAC is bad, my question is, how to replace it?
it looks like the valve its screw in to TB.
All the others valves I have replaced on my cars, has 2 little screws, but not this one.

btw, its a 93 Firebird Formula.
thanks in advance.
sorry for my bad english.

[TraceZ]

My 94 had two little screws holding the IAC to the TB. It comes off really easy.

[Rob B (shoebox)]

Indeed, 1993 IACs are different and screw into the TB.

[TraceZ]

Oh wow, there is a bleeder in there too. I never knew that.

[Injuneer]

I wouldn't jump so quick to the conclusion its a faulty IAC valve. What you see when you hook a scanner to the ECM is the position the ECM is telling the valve to move to. It is not the actual position of the valve you are scanning.... there is no feedback as to the actual position.

Moving the throttle isn't really a good test.... once the TPS goes over 1.0V, the idle speed is no longer controlled at the same position. Watch it while it idles, and see how it reacts to the high or low idle speed. If its idling OK, and RPM starts to move up or down, does the ECM try and adjust the IAC valve? It should. If it doesn't, its an ECM problem.

Shoebox has a "how to" for checking the windings of the IAC valve using an ohm meter, if I recall correctly.

[Ger-Fire-Form-93]

You are right Fred.
The IAC valve should be works only at idle.
but, It was not idling.
well, what i did was unscrew the valve,to find out that IAC was completely stuck on.
I replaced it and after a few minutes of erratic idle the car begins to works fine.

thanks so much Rob, that diagram helps me a lot.
thanks everyone.

[Injuneer]

The IAC does move at times other than when its idling... it opens up as road speed and RPM go up to keep the engine from stalling if the throttle blades close suddenly.