tblock96

IAC Operation

4 posts in this topic

Hi all,

My question is pretty simple (hopefully): How do the IAC valves in our cars work?

I understand the coolant/thermowax, and I know there is some kind of electrical input for a valve/stepper/something. I'm not sure about what that electrical something is on our cars specifically. I also don't know if it's in series or parallel (figuratively) with the wax (i.e. If it's a valve, does it open up to allow the amount of air determined by the wax expansion? Or does it open a different bypass channel?).

Finally, under open loop operation (cold start), is this electrical thing operated, or does it only begin operation under closed loop? Some sources I've found say there should only be air getting sucked up the bypass slot in the throttle body when the engine is cold, and other sources seem to contradict this.

The reason I'm asking is because my car is idling around 1500 rpm when cold (which is not a huge issue, I know) and I know it used to be around 1200. It also occasionally (like once out of every five times I drive it) hesitates like crazy under load, but only when it's cold. There is a high chance that this is being caused by other things as well (I haven't inspected the MAF, there's a whistle I suspect is the valve cover gasket, and the exhaust has at least one leak around the middle of the car), but I'm also just new to automotive stuff and I find it so interesting, so the more I learn the better.

Thanks fellow 626ers!

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1200-1500 is way too high.  Suspect an airleak.  

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By airleak, do you mean a vacuum leak or an intake leak after the maf?

And what is within spec for cold start idling?

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