Its a 1991, F250, 302 EFI, automatic tranny. Runs great at start up, while cold and when the fuel mixture tends to be rich. As it warms up the problem begins, idles rough and stumbles when deaccelerating, not too noticable when standing on the gas pedal. I've cleaned the throttle body and replaced the oxygen sensor. Seems to be some sensor not telling the computer to lean out the mixture or maybe the computer itself. I don't have an easy way to check the fault codes. Any suggestions would be appreciated.

Tom in Seattle

 

I guess the next things I would try would be the Engine Coolant Temperature Sensor (ECT) or the EGR Position Sensor (EPS).


1999 XLT Supercab, V6 5-speed, Astro Eurolid II, MAAP Stainless Steel Nerf Bars, Mobil1.

 

[font size="1" color="#FF0000"]LAST EDITED ON 09-Feb-01 AT 09:00 PM (EST)[/font][p]There is an easy way to check for trouble codes. The link below explains all & even provides code definitions.

http://www.dalidesign.com/hbook/eectest.html

I agree w/ mtucker about the EGR & ECT. Get the codes & let us know what you find.

 

 

I have a 89, 5.0L, F150, EFI, Automatic with the same problem.
try cleaning the Idle air control solenoid that is attached to the trottle body. I have read that this has fixed the
symtoms that you mentioned.
It did not fix mine. I beleive I have compound sensor issues in addition to maybe a weak oil pump. am still trying to fix it.

my symtoms:

oil gauge pegs way low after the engine is warmed up and just put into gear or coming to a stop sign while the engine idles down.
as the engine gets hotter it gets worse. even as i start to slow down in slow traffic the needle pegs low faster, engine light on, and the engine acts like it wants to die like its not shifting down fast enough. The air idle solenoid and TPS seems to measure ok. but not sure if they are sending/receiving the right signals
IN neutral or while the engine is cold (transmission cold ??)
there is no problem.

Did you fix yours?

 

My 72 had this problem. I floored it an it backfired and split muffler from font to back. New plugs, points, condenser, spark wires, rotor, dcap, and carb rebuilt.<br />
These did not solve problem. I had this feeling to recheck distributer. I looked in it and found that the condenser was flopping around like a fish because it was loose. Apparently the former owners stripped the screw. Sure wish I had better vision to see that in the first place. Put in a self tapping screw makng sure it wouldn't hang the advance. It runs like new. Still need to buy a muffler!