I have a 98' Expedition that one day was starting, idling and running good. After sitting a couple weeks....it starts, but won't idle, but runs good. Even after warming up and driving for awhile it doesn't want to idle when you come to a stop???? Any ideas??

 

Try cleaning and lubing the Idle Air Control valve. If that helps at all then I'd replace it. Easy job.

If it's missing at all you may have a plug or COP issue.

 

Sorry to be dumb....but, where is the Idle Air Control valve?

No, it is not missing....runs great...just won't idle all of a sudden.

 

Your cel has not come on?? Does it die, or just shutter, and then come back, and shutter again. 5.4L?

 

The IAC on the 5.4 is on the very back of the manifold, under the Plastic 5.4 Cover, which you can remove to expose by taking out 3? bolts. Passanger side. Little tough to get too, but not bad.

 

The idle is just so low it trys to die or will die, no shuddering. By "cel" I assume you mean "check engine light"....and yes I do have a CEL..it's been on for about a year now.

 

Go over to whichever local auto store you have and get the list of codes it's throwing. I'll bet you have a 171,174, but get them all. Have you fixed the vacuum hoses coming off the PCV valve yet? Your symptoms sound just like mine, '98 expy, 82,000 miles. 2 vacuum leaks, 55 dollars, no more problems.

 

on my 2000 Nav 32v engine the IAC is just under the plastic cover that has the lincoln emblem on it(held as someone said with three bolts)---as you face the front of the engine the IAC will be slightly right of center. It is silver color, about 3in long cylindrical in shape -- maybe an inch in diameter---held in place with only two bolts and there is a gasket---one electircal connection on the end. Mine is easy to get at - right on top of the engine. You can take the IAC off and I spray in carb cleaner in the open end of the valve and then after all the soot is out I usually lube it a little with CRC or WD40---let all that dry and replace it---costs you nothing and if it's not your problem it probably could use cleaning anyway.

As someone above suggested -- check the PCV line too---mine are still in good shape but lots of folks having cracked elbows in that line. Examine very carefully--they can crack where it's hard to see. I've also heard they get soft and can collapse even though they look fine.

 

Great ifo. I will check a those things out and let you know. Thanks to everyone for the input.

 

sounds like the IAC like mentioned above. clean that first, it's a common problem and an easy fix.

 

It will (idle), if you service the IAC.

 

It IDLES!! The IAC valve was the problem....took it off cleaned and lub'ed it and it idles perfect now. Thanks to everyone for all the good info.!!!!

Now for the CEL...still on. I'm going to check the codes this weekend, but Ithing as stated it was a 171 or 174...something about the Engine Exhaut Gas Return...i think? Any ideas on this one?

This web site rocks!

 

Insufficient EGR flow. The EGR is either inoperative or its passages are blocked as well. You might try clearing the codes and see if they return.

 

Where is the EGR?

 

I don't remember exactly where on an Expy, but you can find a silver tube running up from the driver's side wxhaust manifold up to the top of the engine. It will terminate at a t shaped rusted cast iron item (with a circuar diaphragm on top) that is connected to the intake by two studs. That's the EGR valve.