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I have been trying to troubleshoot why my car will drive but not idle. I see alot of posts about cleaning the IAC and it sticking, but I'd like to know how it works.

When should it be closed and when should it be open.

Right now the IAC seems like it is always sucking...on throttle or off

The IAC has two distinct parts. A heat activated clock spring which opens and closes based on the temperature of coolant going through it and a solenoid on top.

Is your idle high? Do you have a check engine light? I've never tested if its open during high idle but it shouldnt matter since its still a metered source of air.

What happens if you unplug the IAC valve electrical connector?

I will try to unplug it....what should happen?

Also...the idle is like 100-200 if it idles at all.....mostly just dies.

When should it close and when should it open...is it a pulse type deal or on and off for a longer duration?.

I think that if its sticking it will be pretty random, meaning nobody can exactly say when it would open or close. As to when it SHOULD, im not quite positive. But I am throwing the CEL myself, and sometimes the car will drop to about 500 RPMs at idle, and sometimes it will randomly climb to nearly 2k. I have a spare one, but I am waiting to do my TD04 to put the new one in, because I don't wanna end up breaking any of the hoses that are near it, and I will be replacing them all anyways when I do the turbo swap.

Well...I took out the IAC, but had to take out my turbo to do it. The little rubber flap was so stiff and there was no gap between it and the metal ring. I cleaned it with carb cleaner and right away it started to pull up, maybe an 1/8" space formed all around.

When the car runs good it will idle perfect and not sputter. I think there is a different problem because sometimes it still will idle at 100-200 rpms and keep dying.

Even though I spent like 4 hours removing and cleaning the IAC and my underlying problem was not fixed, it will be worthwhile in the long run when I do find and solve this issue.

Our issues sound similar, but I'm almost positive mine is just the iac since it's throwing a code, and it just idles wierd. Sometimes it idles perfectly fine, and sometimes it idles like absolute crap. I don't think this is the same problem, but sometimes my cel is on and the car runs fine, other than the fact that IT WILL NOT let me boost whatsoever. As soon as I get out of vaccuum and into boost, it falls on it's face. But most of the time there is no cel and the car runs amazingl.... I'm not sure if thats the iac as well but I'm really doubting it. Are those the same symptoms your having?

Mattheww044 wrote:Our issues sound similar, but I'm almost positive mine is just the iac since it's throwing a code, and it just idles wierd. Sometimes it idles perfectly fine, and sometimes it idles like absolute crap. I don't think this is the same problem, but sometimes my cel is on and the car runs fine, other than the fact that IT WILL NOT let me boost whatsoever. As soon as I get out of vaccuum and into boost, it falls on it's face. But most of the time there is no cel and the car runs amazingl.... I'm not sure if thats the iac as well but I'm really doubting it. Are those the same symptoms your having?

*Bringing back dead post ftw!*

Hey mattheww044 did you ever solve your idling and bogging issue? Mine does the exact same thing, anything more than 50% throttle and it bogs..