Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

2000 F-150, 4.2 PCM Or? Not Truck Or My Fault

Hello (again), once I posted a problem with my truck and with combined wisdom from you guys, I found out my overheating problem was due to the wrong coolant, I put G5 what the manual said and POOF, that was fixed, thank you all. I drove the truck from Atlanta GA to southern MO, with a new a/c clutch, it was getting louder and louder, when I got to my first destination, the guy there was so nice and he had a big garage, he pulled the clutch and sure enough the bearing failed again! then he put the new one on for me and the clutch wouldn’t kick in to make the compressor turn!, but was quiet. He tried to diagnose it and everything went down-hill from there, I heard a spark as he must have shorted something out, the truck runs fine in idle, but soon as you hit the gas, it would miss bad and the automatic overdrive off light keeps flashing, slams into gear (not normal) and misses like crazy. I made it to my second destination (limping) and thought I’d better get away from this guy b4 my truck is ruined. I can do the work myself, just takes me longer because of disability. I think the cam position sensor went out, but why would the transmission be acting up? Can you guys give me a flowchart Idea of what to do? Tomorrow I will pull fuses to check. I have relays also, can they be tested? Thanks for any help. Can I test a PCM?

Honestly, I don’t think I can decipher what you’re trying to say.

Overheating due to wrong coolant? Not likely at all.

You clearly need to check all of the fuses . . . both in the engine bay, and in the cab. perhaps that mechanic did indeed blow a fuse, during the course of his testing

Sorry, I used to have an overheating problem, all fixed. (Thanks to you guys)

New problem - I Had a/c clutch replaced by a guy that seemed to know what he was doing and was just trying to help, after he put new one in, the truck starts and idles fine, but the auto tranny OD light is flashing and tranny slams into gear (never done it before) and the engine misses, is there something that would affect both problems as they both arrived at the same time? Could a cam position sensor do this? Is there a vacuum line somewhere that could have broke or slipped off? I already tried resetting the computer (Unhooked negative cable to battery, turned on headlights and let sit for an hour to drain caps in computer)

Using a test light probe verify that power is getting past all the fuses in the panels under the hood and the dash. Look for any air leaks in the air intake system and check the connections to things around the areas the tech worked to see if anything got disconnected. I assume there is a way to check for error codes for the transmission so check for any clues to the problem.

Something else you can check out is the alternator. To see if excessive ripple voltage causing a problem disconnect the rear connector to the alternator to disable it and then start the engine to see if things change for the better. If so, replace the alternator.

It is pretty strange that the A/C clutch has gone bad again after it was just replaced. Something seems to be wrong in that area.

WALA, I found the problem, he pulled a fuse from the tranny/cms spot to check something and never put it back where it belonged. Fixed, Thanks guys.

Good for you for finding the problem. Best of luck there OP.

It’s the simple things in life that make things so great. Good deal. I still have to wonder about what caused your A/C clutch issue.

Wrong coolant??!! Perhaps changing the coolant you added the correct amount and mixture! Very likely.
Trust a mechanic or don’t, a forum is not going to be better, just cheaper (maybe)

Thanks guys, I just figured it had to be one problem that made so many things go wrong, he put hooked a computer up to the interface in the truck and showed all kinds of codes and tried telling me all these things are bad, so I got my truck outa there and limped to another location to clear my mind and figure out what happened, at first, I thought the computer fried, but before replacing it, I went through the fusebox under the hood (first), that’s when I detected the missing 15 amp fuse! It was the first row 3rd one in just below the a/c clutch diode. I mention this in case you guys come across this problem again, this fuse blown or missing will cause the truck to idle fine, but misses when you hit the gas, also the Overdrive off light will flash and truck lunges forward when put into gear, no overdrive and barely runs down the road, raw gas will come out of tailpipe. (Another one for the books) Thanks for your help and replies, have a great day. David.

The big question: how did the fuse wind up missing?

The second question: why did the missing fuse cause that set of problems? Do you have any info on the fuse? how is it labeled? Which slot is it in?

OP explained above the fuse went missing after some prior shop work. It would be interesting to understand why that particular fuse missing causes the weird idles fine but misses badly on acceleration symptoms though. If it was an ignition system power fuse, you’d guess the engine wouldn’t run at all.