Ok guys first of all, THANK YOU for reading. I originally posted “FUEL SYSTEM HELP”. I figured that out...bad computer ground. I have new problems now. I read a similar discussion that was about 350 posts long, guy had the same issue and never figured it out.
Here is what I’ve got:
1988 F150 4x4 XLT Lariat Fuel Injected 302, Single cab short box, F/R fuel tanks; 55,000 original miles
Background: Grandpas old truck, sat for about 8 years. I got it into the garage, suffered through some electrical issues with the fuel pump relay (bad computer ground). I ended up having to manually ground the #2 pin from the OBD port to get the fuel pumps to operate correctly (2 seconds after key on, full on from PIP signal). Once that was complete, the next step was to drain both tanks (very very nasty fuel) and replace both in tank fuel pumps. Inline high pressure pump is new. Engine started with new gas and pumps! It ran good for awhile (days). It slowly started acting funny, and then...

Current Symptoms:
Starts everytime, but very rough cold idle, sometimes will die, very rich conditions (the code I get agrees, HEGO system rich), but will idle a little better after it’s warm. Shifting to drive or reverse with the brake on can kill it but not every time. Holding the throttle open to about 2000 RPM or so will hold steady but then dip 500+ RPM every 5-10 seconds randomly. Truck will reliably restart. Drives ok, decent power for a 302.

What I’ve attempted:
Fuel injector cleaner in fuel
New MAP sensor
New PCV Valve
New IAC/IABV valve
New O2 sensor - old and new around 5 ohms
New Intake Air Temp Sensor
New coolant temp sensor
New Fuel pressure regulator
New throttle position sensor
New EVP sensor (gave me a position code, fixed)
All new vacuum lines and resealed vacuum manifold on plenum
New Cap/Rotor, Distributor, ICM, plugs and wires (wires greased, placed and routed correctly triple checked, removed to measure continuity and all 8 had 4-6k ohms)
New in-line fuel pump and fuel filter
Resealed throttle body and egr valve
Injector rest (removing one spark plug wire at a time and measuring RPM drop, all similar drops)

What I know I need I to do:
Compression test
Fuel pressure test
Timing with timing light (truck acted like this before I ever touched the distributor but still wouldn’t hurt to rule it out)
Pull plugs and clean/replace after such rich conditions

What I suspect:
some wire insulation is breaking down and showing copper on at least one injector I can see (possible shorting), on the air intake air temp sensor (separated so that’s not happening)

Under the plenum it appears there may have been mice in there (possibly chewed up injector wires). Need to pull plenum and check that seal for a vacuum leak anyway.

Possibly need to bypass the fuel selector valve because that bad gas could easily have gunked it up (a fuel pressure test might show me this)

I read where some guys were having to replace that air bypass valve more than once a year due to low quality valves. I forgot the brand of the new one.

Possible exhaust manifold leak causing the O2 sensor to tell the computer to add fuel?

Worst case - new computer.

Some other things to note:
cats are not plugged - the least I can say without incriminating myself/others
I know I’ve just thrown money at sensors, but I don’t mind because I’m learning this truck and there were 30 year old sensors on it. I want it to be reliable. After all it only has 55k miles on it.
I think I have a wiring issue, but I’m hoping for someone here to enlighten me even if only about how to test some of that.

Thank you all for reading. I know it’s long but I wanted to get all the info out there upfront to try and shorten the later conversations up.

88150guy

https://www.ford-trucks.com/forums/8...nd-bad-30.html
this is the link to the long post. I take back what I said, Kart18 eventually changed timing chain and gears. He was at 160k miles though. I shouldn’t have to do this yet!

The sensor, for the computer. The switch/gauge does fine so I left it alone.

Ok, thank you for the advice. I’ve had it out before searching for that exact item but it was fine. This was before though when I was looking for my grounding problem. I’ll pull it again and check it out. I’m gonna pull the plenum and check for cracks, seal quality, and probably tear down the emissions items behind it and inspect them. I read where the adapter for the tube off the EGR can crack and cause a major air leak. Thanks again. I’ll update when I get this done.