Originally Posted by Nick

Since the problem only happens when it's real warm out, it hadn't been an issue until just recently. So I finally got around to looking at it. Borrowed a Snap On scanner and checked for codes, none found. Ran a Key-On-Engine-Running test, everything checked out fine. Gave some thought to when and how the problem actually occured, mainly after a moderately long run at highway speeds, in warm weather, only once I got off the gas and slipped the trans into neutral, while slowing for an off ramp. That's the only time the idle would stumble, and usually the engine would stall. Decided to replace the EGR ($100 from Ford). Since the EGR does nothing when at hwy speeds, and only kicks on when rpm's come back down, I thought maybe it was sticking, and that's what was causing it. Also, I took the time to remove the snorkel and clean the throttle plate by hand (was rather dirty), and removed and cleaned the mass airflow sensor. I have a K&N, so it's possible that oil migrated from the air filter and found it's way to this sensor. Anyway, not sure if the weather will be warm enough for the next few weeks to trigger this problem (Mr. forecaster says a return to more "normal" temperatures is expected). May have to wait until June or later before I'll know for sure. Either way, everything I did won't hurt...