Ford Repair: ford engine trouble, upper intake manifold, air control valve

Question
I have a 2001 Ford Expl Spt Trac with the 4.0L engine. I used the car yesterday and it worked fine. When i went to use it today the engine would turn over but not idle. I can keep the engine running if i rev the gas but as soon as i stop, the engine dies. I'm not leaking any fluid. I think that it might be an airflow problem but i don't know how to tell and how to fix it.  

Answer
This is a common problem.  For years now, the idle has been controlled by the Powertrain Contol Module. It uses the Idle Air Control Valve (IAC) to control a small amount of air entering the engine to adjust idle speed.  It is mounted to the upper intake manifold with two small bolts, and has a small electrical connector on it.  It is about two and a half inches by five inches.  It may be stuck closed, you can remove it (be careful, it may have a paper gasket) and clean it out with an Air Intake Cleaner.  If this doesn't help, it may have failed, and need replacing.

I hope this helps,
Dave