Looking at your first post, when the check engine light came on, there usually isn't a code for a bad IAC valve, or at least my experience on this forum is no one got a trouble code for that particular part. What would help is to know what the code was, or what the code is now. There are a many codes but it will start with "PO---". Example would be "PO305". You don't need to know what it means, There are those on here that can look it up. Sometimes a code leads right to the answer, sometimes it's a symptom of something else wrong.

At this point I guess I would do this if it were me.

1. Disconnect the car battery at the negative for 15 minutes, this resets the computer to the factory settings. See if that makes a difference.

2. If you had someone put the part on for you, make sure it's the right part. This happened to me on another part. the box showed it to be the right part, but the part inside the box had a different part number and made my Escape run really strange.

3. If you are sure it was the right part, and you still have the old part, put the old part back on, and see what happens. If it goes back to running like it did before, it's possible it's not a bad IAC, or the one you replace it with is bad (not common but it does happen).

4. If it's drivable find out what the check engine light code is. You may have to do that first, when you disconnect the battery it may erase that code. But if it's idling at 3000 rpms, that's not a safe driving condition.


Sorry, I know this is frustrating, some times it's easy to diagnose a problem, because it's a common problem, other times it may not be possible on a forum, with limited information.