jajaredneck

I Have a 93 F150 with a 5.0 in it and have an issue starting once it is warm. truck runs fantastic when cold warms up still sounds great no issues. If shut off it will not restart until cooled off. has a new distributor, plug wires, plugs, and coil. have checked the fuel pressure at the rail both cold and hot to check if a pump was failing when warm running 36 to 38 lbs consistently. Have replaced IAC Valve and cleaned EGR. Had a check engine light when at operating temp until i cleaned the EGR valve. it has not come back on since. have pulled several parts off another running truck to check for failing parts including ECM, Ignition module, and TPS sensor. It Seems to me that maybe something electrical is warming up and failing. i dnt know enough about how sensors work to know where else to look. i plan to swap in a new O2 sensor tomorrow but my understanding is that would cause a running issue if not working properly and when running it runs perfect. Any Ideas?

Matthew Burr

2 things, go get codes pulled and have them print out the results. that would be a start, second, do you see white smoke out the back at all? you may have a coolant leak thats presenting itself after the engine warms up

jajaredneck

At first there was a check engine light. i cleaned the EGR valve and heard a rattle when shaking it which i was told was a good sign it was ok. upon re cranking it i have no light. can a shop pull up stored codes on a obd1 system? i ran the codes with a meter according to the book found no codes present or stored. and there was a little smoke earlier in the project, just finished rebuilding the top end due to poor compression on cylinder 7 cause of a stuck valve, but the smoke was due to a intake manifold leak that has been since fixed. when i bought the truck it would not crank due to turned fuel in the tanks i replaced the tanks, pumps, lines, injectors and regulator. i am now getting good clean fuel to the rail and power to all injectors, checked with a node light cold and hot. im not losing spark either cold or hot. my research points to a IAC valve, i swapped it out with another one i had and no difference. both valves checked out for resistance and the harness checed out with 12.6 volts which is in range according to the book

Matthew Burr

No codes, relevant sensors check out, problem is when warm, I would double check sensors when it's warm if you haven't done so already, and I am still leaning towards a Crack or defect of some sort opening up and ruining your fuel air mix, ie intake manifold crack/warp or head/gasket. Hit it with a can of carb cleaner when warm and see what happens

94_f150_ga

There's a coolant temperature sensor that was causing this condition on my '94. Would start right up when cold, but when warm would take forever. About 20 bucks or so and easy to replace.

Sulli8888

My coolant temperature sensor was making mine flood out and hard to start. the new sensor fixed it