I have a 86 f-150 with a 302 FI V8. Here is a summary: My truck kept stalling/loosing all power whenever it warmed up to normal Temp. and whenever I went over 3,000 RPM. I had fuel pump replaced in engine, didn't work, then I replaced the one in the tank. It now runs better under a load (over 3,000 rpm) but it will not run at idle at normal temperature now??

I checked the battery and alternator and both are fine. Once the motor cools back down, it will crank again and run fine until the engine warms up to normal temperature? Does anyone have any ideas what this might be?

Thank You!!!

 

Have you replaced the fuel filter? Try replacing your O2 sensor, sounds like it could possibly be bad since its dying out when it warms up.

 

Pull the codes.

You can also try to unhook the vac line feeding the EGR valve and plug it. Run it and see what happens.

Here are some links for the codes:

http://www.troublecodes.net/Ford/

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

I found the analog meter to be the easiest to read.

 

I can only guess since I missed about 20 years of automotive progress but let me say this. The vehicles in my day had an automatic choke that was a spring that would change as it heated up and adjust the throttle on the engine for the correct air/fuel mixture. Todays vehicles seem to know the engine temperature and adjust the length of time that the injectors fire in order to maintain the correct Air/Fuel ratio.

It sounds like your Air/Fuel ratio may be incorrect when the engine warms up or some other component starts to fail when it heats up.

Another problem that can occur is vapor lock. The gas in the gas line can get so hot that it changes from a liquid to a gas.

http://autorepair.about.com/library/faqs/bl828.htm

 

Is the engine shutting down just like you're turning off the ignition? I had a problem like this with my 88 F150. It had a 300 I6 with the coil mounted to the engine. I finally found out that the coil was cracked and when it got hot, it would short out internally. The fix cost me about 12 hours of my time, but only $38 for the coil.

Hope this helps you,

Sidewinder

 

Thanks everyone for the help! I will try looking into to everyone's suggestions and try to figure it out. Maybe I can come up with something.

 

I forgot to say that I have already put new fuel filters, O2 sensor, pcv valve, rotor button, plug wires and plugs and nothing new. Just thought this may help

 

Almost sounds like you're having old fashioned vapor lock. Replace any of the hoses/lines recently?

 

No I haven't replaced any of the hoses or lines. I will probably do that next.

Thanks for the help

 

Did you try the suggestion about pulling the vacuum line off EGR valve and plugging the vacuum hose?

The way I understand it the EGR valve does not start working until the engine is warm and the rpms are high. If the EGR valve is open too wide then the engine may stall/die/quit running.