Heres the run down, I bought the truck about a month ago its a 1990 F250 4x4 5.8L 5spd. Since, I have had multiple problems... no start, overheating, dying after a mile of running, and now running like an old "lawnmower". Heres a run down on the parts ive replaced. Battery, starter, alternator, coil, dist. cap/rotor, spark plugs/wires, TPS, PIP, Coolant Temp Sensor, both fuel pumps, fuel filter, fuel pump relay, thermostat, thermostat housing. Now for the Situation, Last night i drove my truck about 80 miles threw out the day and had no problems, went to the car wash last night got her all cleaned up, drove home (about 12 miles) them decided to go for a little cruise, about 16 miles. It ran great the whole night. I go to leave for work this morning around 7:30 which is about a 25 mile oneway trip. i noticed right away my truck was running a little funny. almost like it had a choke on. no power backfiring and sputtering the whole time. yet it would idle fine. i stopped checked plug wires and they were fine. i continued on my way and by the end of my trip i couldnt hold 1,500 rpm in 5 gear. thinking i had moisture in the dist. cap i removed and sprayed a little wd40 and wiped dry then let it sit for a couple hours. didnt help. after work around 7:30pm i took it straight to oriellys and tried to run codes, none popped. tried to check timing using a OBD1 Scanner, it woudnt complete the test (tried 6 times). i then check my timing chain for unordinary slack yet nothing outta spec. drove it another two miles to the gas station and let it sit for about 2 hours, when i returned and tried to leave, it limped for about 100 yards then died and wouldnt start and check engine light turned on, i was thinkiung it may have been a fuel pump issue so i switched tanks and let it sit for about 10 minutes. it started but continued running horrible "no check engine light". i am out of ideas, any thoughts would be greatly appreciated.

 

This is only a guess based on my past experiences, but it sounds like the computer or PIP.

 

Many times the pins on the diagnostic link are corroded making it difficult to check for codes. I suggest cleaning the pins using contact cleaner or a little aggressive approach such as a small screwdriver or fingernail file. Have you tried using the jumper method with a piece of wire to check for codes?

With the laundry list of parts you already threw at this problem you may have introduced more variables. A spark tester and fuel pressure gauge may have narrowed down the root cause without all the parts.

 

I am also no expert but it sounds like timing. My El Camino had similar problems a few days after adjusting my distributor. I didnt tighten the dist. hold down and it slowly twisted out of spec making it run more and more horrible.

 

Just to clarify all have the problems have happened one at a time not all at once. I was messing around with the distributor and it's right on point, but the problems the same. Is there anyway the fuel filter could cause this? Or is it more likely electrical? Could it be a relay or the ECM?

 

Have you been able to read any codes, rla2005 explained to clean up the contacts. I think your problem is electrical, but codes may isolate that for you. The car wash may be a factor, did you look at the ECM wire plug for water staining, water may have ran down the fire wall. You could buy a very good code reader for about 30. bucks.
Amazon.com: Equus 3145 Ford Digital Code Reader: Automotive...I have this one, it sure can be handy at times.

 

Okay, first off, only replace parts, especially electrical parts when you have tested them with a multimeter, throwing parts at it will only result in your wallet getting lighter. One thing you must remember about these trucks, A bad ground will cause intermittent electrical problems. The computer on these trucks grounds itself by the outside of the metal case that houses the computer. If that case is not grounded, and you put the code reader on the computer, you will not be able to pull any codes. I found this out the hard way. On these trucks there is a white plastic piece that holds the computer into the kick panel, on this white plastic piece, the xlt models had a metal piece that is attached to the plastic piece. This helps the computer ground to the body, if its missing the case can have problems grounding to the kick panel. I would suggest that if the code reader won't read codes, push on the computer case and see if it causes the case to make the ground and complete the circuit. if it does run a ground wire to the case.

 

All parts i replaced were to fix existing issues. I have an OBD 1/2 scanner. The test Ive ran have been. KOER, KOED, Wiggle Test, all completed and passed. My scanner has a timing check and cylinder distribution test also, both test would run( they were increasing decreasing idle and such but wouldnt show the the results. I then called a local ford dealer and asked them for some help, the master tech told me the test not completing is ordinary because it's a hit and miss kinda timing check. I will check my grounds, the wires and computer bezel when I get off work, thanks all

 

Ran fine, next morning a problem, no codes or light. I still guess computer or PIP, you could put a fuel pressure gauge on her to see what you got there, since that question seems to be on your mind. When I was having the same type of problem as you, I drove around with the fuel gauge hooked up all the time, jumped out to read her at first sign of poor running...I know that you changed the PIP already, but I went through 4 of them in a 1 week period. Numbers 1 & 2 would run fine but fail when hot, run again when cool. Number 3 would run fine at idle but terrible at any higher throttle input, all 3 were rebuilds, they gave back my money and I quit the rebuilds. Number 4 a new manufacture was the keeper, a heat tested unit and so far no problems at 5k miles. You certainly could have something else going on, a tough one to isolate though with no codes (computer problem?). I also like to time her by using a vacuum gauge, you might want to try that, disregard the carb advice.
Vacuum Engine Timing | MILEPOSTS Garage (Tech Tips)

 

Yeah I tried a used my "old" new PIP and it problem continued. The thing that's really puzzling me is that the problem is there on initial start up. And the longe it runs the worse it gets but it never gets any better nomatter if you let it sit for a day or an hour it just consistently goes down hill, which to me sounds like something mechanical in nature instead of electrical. I will continue into checking out all ideas above and to come. I'm completely clueless!!!