When i start my truck while its cold, it will start and run fine until the warm-up process is done and when it starts to idle lower, it stalls.

And when it is warm, starting is also a problem. It will act like it doesn't want to start, it just keeps cranking. Could that be the coil going bad?

Thanks!

 

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Could be a lot of things and is likely more than 1 thing. Bad idle could be a dirty IAC, take it off and clean with carb cleaner. You should also check the fuel pressure at the rail, if you're not getting 35-40psi when cranking you have a bad pump or clogged fuel filter.

 

Also, read the codes from the computer and see if it has any. The efi engine is very complicated, but the good thing is the computer can "see" if any of the sensors are obviously bad.

 

This is what it does...

YouTube - EFI 302 problem.

 

I believe Conanski is right on as how to start trouble shooting. The only thing that I would add is: I had a fuel pressure regulator problem that would allow my engine to start when cold, but after it warmed up during a trip to town; I would park it and shut it down and wouldn't be able to start it until it was completely cooled down. Turned out to be a bad fuel pressure regulator. Very similar to your problem.

 

That is probably the problem then. Because after it warms up and i turn it off, it doesnt start easy. Thanks!

 

This is what it does when it is warm...

YouTube - 1985 Ford F-150

 

looks like iac problem on the video.The throttle body is clean, right?

 

Don't use CARB cleaner, it is harmful to the coating in the TB and intake on Fords, Use throttle body cleaner. They are different chemicals.

 

I dont know, ive never touched it before. Where is the IAC? Should i clean them both?

Okay, thanks for the info.

 

Dont forget to check your fuel pressure regulator. It can make it act funky too.

 

The IAC is bolted onto the side of the throttle body. It has a shape of a small cylinder with an electrical plug on the end. If you haven't touched them before and it has some miles on it (whose truck doesn't, especially our years); its time for a good cleaning. Clean both the throttle body and IAC. You need to remove the IAC to clean it properly; and use a tooth brush with the throttle body cleaner if needed to get them both clean. I noticed a huge difference in idle quality and low speed driveability after cleaning them.

 

The TPS caused those exact symptoms for me. I had to unplug it to crank it, then plug it back in after it was running. I replaced the IAC first, didn't change a damn thing. When warm, when unplugged, does it idle really high, but run a lot better?

 

Where is the fuel filter and wehat does it look like?