Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
The car uses an IAC (idle air control) motor on the throttle body and not really a choke. If the car starts fine both hot and cold then this is working like it should. If you had a mouse in there, I would look at the rubber hoses. If you have an intake leak or some other vacuum leak, the car will start up at high idle to try and make the proper fuel mixture when it's running. A vacuum leak will cause it to continue to add fuel to make the mixture right, and this will cause high rpms.
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Thought it wasn't coming down?
If it does come down, then it's likely the IAC is sticky and covered with carbon. You can remove it and clean it with carb cleaner. Also make sure you clean the throttle body where it goes as well.
If it's coming down, then scratch the vacuum leak theory, this won't be the cause.
I am sending you a diagram of the IAC location to help.