car start up fine ,you run it for a while and at stop the idle will go up and down and turn off, check for vac. leaks and every thing is ok

 

If there are no vacuum leaks, check your catalytic converters.

A good test for that is to check vacuum at idle to get a static reading. Next have a friend bring the car up to around 2500 rpm and hold it steady. You should drop vacuum. If it starts creeping back up, it's a good indicator of a blockage in the exhaust system.

This "could" cause idle as well as performance and fuel mileage issues.

 

Could also have a bad idle air contol valve. Scan the engine computer for codes. Unplug the IAC and plug it back in (connector may be dirty). You could also try to disconnect the battery for a few min and reconnect. If all the above is okay and it is not fixed take it to Ford and they can reflash the computer to fix it. A friend of mine had a similar problem with a Ford Crossover Vehicle and the reflash fixed the problem. It was doing the exact same thing as yours. No codes or any other indication of anything wrong. Hope this helps.

Bob

 

Clean the throttle body, particularly where the blades meet their openings. Remove the air intake from the TB, wipe in there with a clean rag sprayed with a cleaner designed for coated TBs. I had the same issue, cleaning the TB resolved it.

 

I agree clean the tb, mass air sensor, and idle air control and all the connections for these parts.

 

Because of the fly by wire throttle these cars don't have an IAC valve. When I started having idle problems it turned out to be a bad throttle body. However , my idle problems were when I let off the throttle and was coasting , instead of dropping to a little above 1000 rpms and holding till I stopped , it would drop straight thru the base idle and stall. I was also running a little lean and when I changed the throttle body both problems went away. Like was said above though , you should first clean the throttle body and mass air sensor , do a search and there's a thread on the correct way to do this ...

 

Clean the throttle body and maf and every thing is normal again thank's every one