I live in Florida,if the 98 f150 4.6l sits in the heat(the truck is Black) when I crank it up it will stall. I crank it up again I have to rev it to about 3000rpm and keep my foot in it going down the road if I have to stop- it stalls. Crank it again run it down the road it will run fine. This only happens in the summer. It is getting hot here already and it has happen five times this spring.

 

This might be it, look at the Frequently Asked Questions Post at the top of the list for more info.

Q: My truck idles roughly or stalls at idle. What could be the problem?

A: A fairly common idle related malfunction in these trucks seems to be the Idle Air Control valve motor. This valve sits on top of the throttle body and holds the butterfly valve open at idle so the engine can breathe. A sluggish or malfunctioning IAC will prevent a constant idle. The problem sometimes only presents its self when the engine in cold. This certainly isn’t the only thing that can cause a rough idle, but If you find yourself having to keep pressure on the gas pedal to keep the engine running, this may be a place to start. Typically, just cleaning doesn’t offer any improvement, if the IAC is faulty, it usually needs to be replaced.

 

I work construction and might have to drive fifty miles to a job and when it sits in the sun till say lunchtime is when it will act up. The next day if I park it in the shade it will be fine. A mechanic that I built a room addition for said it is the cold engine temp sensor. I took the truck to Ford for the famous "p0401 problem" Ford wanted $900 and change telling me it was the DSPE sensor. This mechanic fixed it in his yard while I was working on the addition in 45 minutes for a $100. The ports were full of carbon. So what I am getting at is I trust his opinion. I have I read a lot of your posts and you know your Fords. Any other suggestions or try this first? Some of the posts said this is a costly part?

 

Hey triton I drove from Tampa to Perry Fla)about 225 miles)today got out to go in to eat and came out the truck wouldn't idle again same as the above post. The truck sat infront to the resturant maybe 30 minutes and it was hot out today approx 90 degrees. You really believe it is this IAS motor. Is that the coil looking thing sitting on top of the throttle body?

 

It was a suggestion, I don't know if that is the problem for sure. Hopefully, Racerguy or one of the other guys will post some other things to look into.

Have a good Memorial Day

 

IAC sounds right. i had it happen on my sho. the heat agravates the problem. after running for a little while the hurricane that the fan produces cools it off and starts to function properly again. this will only get worse. although could be as simple as a dirty plug connecter at the IAC. good luck

 

Try cleaning the electrical connector, but if it doesn't work then try
cleaning the IAC with the carb cleaner. If it works at all, it probably
won't last long, but at least you'll know the problem. It's $55 to $70
for the part, I forget which. It's not throwing a code at all?
I know on the Expy, I had to keep the gas in when starting, and had to rev
it to keep it running. On the F150, it idled up and down very badly. Good luck.
p.s. I twisted a screw off in the IAC when re-installing, had to remove the
throttle body again and get a screw back out kit. It's an aluminum motor,
I'm lucky I didn't screw up the threads in a bad way.

 

That exactly what it is doing!!!! Now what part is the IAS?

 

Idle Air Control is located near the throttlebody on the intake. It should have (2) 8mm bolts holding it on and a 2 wire plug on it.

 

OK gang I cleaned it and boy was it dirty. I looks like a "C" size battery with 2 bolts and 2 wire connector on the back. I tookit off and there were two ports in there. One port was really dirty the other hardly anything. Inside there was a shaft with a spring coiled around it. looks like the little motor or solenoid must energize or something and allow air in both those ports. The back one was dirty the front not. It idled at 1100 rpm upon cranking idled down to 900rpm after running a minute.Does this sound correct?

 

bout right