Thought I'd throw this out there to see if anyone might be able to help me zero in on the likely problem. My 2000 Regal GSE (208K) has run fine until last week. (Well, new idler pulley last month, but no trouble at all since.) It won't start without the accelerator, and stalls IMMEDIATELY when I take my foot off the accelerator. (I could drive around just fine if I felt comfortable driving an automatic with two feet, one always on the gas.)

The car seems to run just fine. The start is a little rough (like maybe it's running a bit rich?) but smooths out, and would keep running if I could just keep my foot on the gas all the time.

I understand this might be a bad idle air control valve, or a bad/clogged EGR valve, or perhaps a bad O2 sensor, or a crankshaft position sensor...

With all these possibilities, might someone have a little insight to help point me in a likely direction, or a sleuthing strategy? Right now I'm inclined to start with the cheapest part first. I'd like to be a bit more methodical about it.

You don't have to replace the IAC valve, just remove and clean the carbon from it . Don't disturb the pintle depth .If it is pretty clean then replacement may be in order. If you remove the EGR valve you may be able to see the problem if any of the solenoids are carboned up and stuck open. Then if you see that , it would need to be replaced. (Not cheap) maybe $200.00 I don't believe the crank sensor or the O2 sensor are suspect at this time. A good idea is to see if there are any codes in the computer that may help narrow this down to a specific system for you.

Finally an update.

We decided it might be the EGR valve, so we took it off, cleaned out the carbon with an air compressor, and popped it back on the car. Voila! Car runs fine again. Great idle, with no funny business. It may be a temporary fix--until some more carbon gunks up the valve--but for now, it was the right fix at the right price. Thanks for your insight, hanky!