My 92 F150 has a few problems. first off it doesnt like to start when the engine warms up and it misses slightly at idle and while i am driving at cruising speed in overdrive. ive replaced coil, plugs, wires, cap , rotor, coolant temp sensor(which tested out bad) air filter, battery, fuel filter, and seems to have good fuel pressue becase when i releived the system of pressure at the schrader valve the fuel had alot of pressure not sure exactly how much but seemed like enough for it to run good. I am at a stand still and cant think of anything else. the only thing i noticed that didnt seem right was when i changed my air filter thier was oil in the bottom of the airbox. this problem probably doesnt relate to the problems i am having but it didnt seem right to me. Ive also checked all the codes and i came up with nothing. Any suggestions would be great thanks everyone.

 

Thinking the EGR system can be one of the causes for the problem you describe - but this problem usually throws a code when the computer detects that the valve isn't positioned where it should be. One other thing is to inspect is that the exhaust supply tube to the valve to the intake plenum is intact - no splits in the tube, loose or broken fittings, failed gaskets, etc. - so that air instead of the desired oxygen-depleted exhaust gas would be introduced into the intake plenum.

If your computer scan revealed nothing, that lets the oxygen sensor off the hook, for now.

There are also resistance and voltage checks that can be done with a multi-meter to see if the TFI and stator modules on the distributor are within spec. Just for grins, may want to check the distributor shaft for any excessive 'wobble' which may open rotor blade-to-cap or stator pickup distances beyond spec. Suggest to check these items out first before checking into the EGR system.

Also, my 'blinkie-light' Actron scanner-for-dummies has a feature to identify weak cylinders - you have to flip the switch, turn the ignition switch, and do some things in a particular order to get the scanner to tell the computer to go into this particular test mode - but this test might be another opportunity to narrow things down if the miss is related to one or a few cylinders.

I've noticed my PCV breather filter sometimes gets saturated with oil - the only thing I can think of is the PCV valve isn't isolating completely under low-vacuum manifold pressures - allowing oil vapors to creep out the air supply tube, condense on the tube walls, then ooze on down to the filter.

Good luck, and keep us posted on what you find.

 

thanks for the input. i will give it a try tomarrow and see what i come up with. i also read tonight that the fuel pressure regulator could cause this type of problem, so i guess i will have to wait and see once i test it. but thanks again for your help.

 

Might want to have the ignition module tested also.