Do check your intake manifiold gaskets.

But I did replace my IAC valve last year after experiencing similar symptoms. Start it up revs up to 3-5 grand and scares the poop out of you.

I got a great deal on e-bay for like 25 buck on an auction that no one else bid on. and its 5 minutes to swap it out.

You can also check it with a multi-meter. I don't have my book with me to know what its supposed to read though.
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when looking for a container to hold drained brake fluid, find a container that is different from the beverage you are currently consuming.