I have a 1999 F150 with a 4.6L and recently probably once a week it wouldn't idle when I first started in the morning. Now it won't idle at all. I cleaned all the linkages around the throttle body but no help. Otherwise the engine runs fine. Any ideas? Thanks in advance.: :cool:

 

IAC valve or TPS sensore

 

Ditto, especially on the IAC.

 

Could also be the EGR valve or the MAF, but I would definitely check the IAC first.

 

check the IAC, it can surely cause the problem.. it that check oute then you need to remove and inspect the PCV hose... it will be insulated, but the hose is actually a hard plastic, where the hose meets the PCV valve there is a small rubber elbow. you have to pull back the insulation to see it... this elbow gets worn, and it will collapse when the engine is providing vacuum to it... usuall when the engine is cold, the rubber has expanded enough to allow some blow-by-gas to reenter the combustion cylcle. once the engine is somewhat warm, the rubber elbow becomes weaker and collapses... therefore causings the rough and unstable idle.... this happened to me, and i replaced a ton of stuff(IAC, EGR, DPFE, and TPS) before getting this info from this site... however, my truck never set a code... so if no code is set, its worth your while to look at this, new hose and PCV valve all come as one from ford, for around $25... hope this helps

 

one more thing, you may want to invest in a Haynes manual, and and voltage meter, its money well spent... this way you will be able to test the TPS, EVR solenoid, MAF, etc.... before replacing them... most of these senors run $50 a piece, and that's autozone prices... so you'll come out ahead, but spending a few buck up front on the meter and the manual... not to mention, the manual is pretty descriptive....

 

I have the same problem. I have a 1998 f150 with a 4.6. Occasionally my truck will not idle. It runs fine other than that. If I drive it down the road for 5 minutes... it idles fine. I believe the problem to be the Idle Throttler Valve. It sits on the top backside of the throttle body. I went to Ford and they want $125 for it. I decided to wait until it wouldn't idle anymore to replace it. Hope this helps.

Oh, my brother is a service manager for a Ford dealership, he also thought the ITV was more than likely the problem.

 

Thanks for all of the help guys! The problem was my idle air control valve like some of you suggested. For anyone who is curious, a new motorcraft part is ~$120.00. O'reilly auto parts has a Borg Warner brand for $45.00.

Thanks again for all of the good advice. This was my first problem with this truck since I bought it new. Time to buy a repair manual I guess.

 

Why spend the money? Just take it off and clean it with some parts cleaner and then re-install. I did this to mine about 20,000 miles ago and no problems since.