It seems strange to me that a pintle going in and out of a little hole in the side of the throttle body could have such a big impact on idle speed. It seems like if you have an open air cleaner with a lot of airflow, that little hole where the IAC is couldn't make any more difference. What principles are involved in the working of the IAC? What specifically tells it to extend or retract? Why?

 

it's controled by the ecm. it is part of the air fuel management system along with the o2, tps, cts, maf, and a few others. they all provide information to the ecm and it makes adjustments as needed to the a/f and timing.

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ICON Motorsports

1st & 3rd
MM Black Diamond 538 F&AM

 

Doesn't seem like opening that tiny hole would do much?

Well, if you think about it, the valves on the throttle body don't really open all THAT much from idle to WOT... so the small IAC valves could easily control a couple hundred here or there.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

No, it really does'nt seem like it could. But obviously, it does. I was having problems with a rough idle and almost stalling it was so eratic and low. My car is not stock. Got a 383 in it and a 305 throttle body with 350 injectors. I bought a new IAC thinking it would fix the prob I was having, but it did'nt. So what I did was buy some gasket material, made 4 gaskets for the IAC and stuck them on there. Now, the pintle is not able to reach as far as it did before and the car idles smooth and steady and takes off better. Some people may say that doing things like that is dumb, but people put spacers under throttle bodies to improve performance. When there is almost nothing stock on a car, sometimes OEM replacement parts need to be modified to make stuff work.

 

You do know that you can push the IAC in instead of adding more spacers.

 

I did that but it did'nt make a difference.