87 f-150

Will eventually start and run very rough.Stalls when accelerator is pressed.Good compression, new computer,new plugs,some plugs are wet and some are dry.Ran for a while with very high fuel pressure.What could be my problem.How can I check these other possibilities.

Fuel injectors needing cleaning my best guess. 3M makes a few kits that can help if that is the problem. Is it fuel injected?

I used to be wrong sometimes when I just guessed that it was the timing chain. Which engine does it have?

It ran for one day after having a couple sensors replaced before the high fuel pressure was discovered.

302.The rotor spins when the engine cranks.

Mileage?? Rotate the engine by hand, forwards and backwards, while you watch the rotor. That will give you an idea of how much slop is in the timing chain. If you can rotate the crank 20 or 30 degrees before the rotor moves, I would suspect it’s jumped time.

87 wasn’t the best year for fuel injection on Fords. See if your model has an inertia switch which tries to disconnect the fuel pump if you hit something hard enough with the truck. Sometimes a big pothole can cause the switch to go halfway. I don’t know if the pickups had these switches but the owner’s manual should say. A big enough bump would make my 87 Tempo run bad until I pressed the button on the switch. Mine was in the trunk at the top of the left rear fender. The throttle position sensors in 87 were trash too.

The problem you are having can be caused by the MAF sensor or an air leak into the carb body. See if the tubes are connected right.