I was checking and adjusting my timing today and noticed that when I jumpered my A & B terminals on the diagnostic port, the IAC valve started making strange clicky noises like crazy. I unplugged it to be sure and it stopped. For reference, it is a brand new IAC valve. Is this normal?

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My Fiero: 1986 Pontiac Fiero GT, V6, 4-speed manual

Did the clicking stop once you started the engine?

I'm not sure, the noise of the engine drowned it out.

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My Fiero: 1986 Pontiac Fiero GT, V6, 4-speed manual

Anytime you complete that diagnostic circuit you will hear a lot of different noises like relays and the fuel pump and maf sensor kicking on and off. The iac is part of the closed loop after the car has warmed up. You can't hear it while driving because of engine noise. Start the car and open the trunk after the engine has warmed up. If it is making that noise after warm up then I would be concerned.

GM foolishly made shorting A-B do multiple things. One of them is with the key on engine off, the ECM continuously moves the IAC to the closed position. Now that doesn't create a problem of burning out the IAC because the IAC is a stepper motor. The one slight problem that it does present is once you start cranking the engine the IAC is fully closed and that makes the engine hard to start without using the throttle a bit. Once the engine is started the ECM no longer preforms the "close the IAC" function.

On later years (after Fiero) GM dropped this foolish function.

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You won't be hearing any noises from the MAF (read above) because the Fiero does not have a MAF.

[This message has been edited by phonedawgz (edited 09-13-2015).]

quote Originally posted by phonedawgz: ...a problem

Phonedawgz, you're a knowledgeable guy and you're often quite helpful here... but why do you continue to take money (and harnesses) from customers and then terminate all contact with them, as reported HERE? And this is far from the first time it's been reported that you've done this.

Why are you stealing from members of this forum?

This makes absolutely no sense!

[This message has been edited by Patrick (edited 09-13-2015).]

www.youtube.com/watch?v=GEGItKeg970

On GM carb cars the short function would drive the IAC out and in, repeat. Kind of looked like the IAC was trying to have sex with the throttle.