Mu 2000 5sp GT stalls if I have her in neutral for a few seconds after running at highway speeds. Idle dips, fluctuates, and eventually stalls out. Engine runs perfect at any other time. Cleaned the IAC in case that's what it was, still doing it. Has new plugs, PCV and fuel filter. Only engine modification is the addition of a K&N by previous owner. Doubt this is the problem. Can anyone help?!!

 

Most likely a bad IAC, in which case cleaning won't help. Does it only do it hot and on off ramps.

 

Thanks for the quick reply. Was leaning towards replacing the IAC. Nice to know someone else thinks it might be it too. Yes, it only happens on offramps. Yes, the engine's hot when it happens.

 

Possibly a sticking EGR valve, I'd run it unplugged and see how it is before changing the IAC.

 

Ive had issues with other cars (not the stang) shutting off because the coolant is overheating when the guage did not even showing hot. Just an idea.. I'd check the EGR before doing the IAC too.

 

I would say one of the two.
Did you get it fixed?

 

Fuel pump driver was the problem on mine when it did the same thing.

 

I was going to say weak fuel pump....could be lots of things, probly something stupid like always.

 

Did you find out what it was?

Sounds weird , so your saying it only happens on on/off ramps?

 

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...