I have a '94 F150 short bed 2WD with a 4.9(300) straight six and 5 speed Mazda transmission. I Have only had it for about 2 months. I traded a horse for it. It ran great for the first 3 weeks. Decent mileage, about what it should be. One morning it didn't want to start. I gave it a shot of ether and it fired right up and ran, but idled some what low and a little rough. The mileage also dropped considerably. Once it had been running it would re start no problem. Also it no longer accelerated normally. If I pushed the gas very much it stalled out. If I accelerated very slowly it would make it up to speed. Also, it would loose power and speed going up the slightest hill.
My experience with wrenching ended around 1988 and my last real project was a '67 Ranchero that I put a 351 and C6 into. I have no experience with the 'later' models with fuel injection and computers, electric sensors etc. I called a friend that does have experience for help.
Upon inspection we found several dry rotted vacuum lines and loose fittings. The truck is all original and in remarkably good shape, with only 94K original miles. After replacing the bad lines that we could find the problem persisted. Mean while the clutch went out.
I know that the 2 issues are not related.
It is currently docked in my garage. If all goes as planned the clutch will get replaced in the next few days.
Before the clutch quit, while driving it, the fuel mixture problem, rough idle bad mileage poor acceleration etc. would intermittently go away, suddenly. Like if I hit a bump it went normal until I hit another bump. This makes me suspect an electrical short, possibly to a sensor that controls the fuel mixture.
As I said, I have no experience with the more modern, (by my Olde School standards. Hey, it doesn't have points or a carb) fuel control systems.
I had a couple of shops plug it into their system readers and none got a code that they could decipher into anything useful. Also both fuel pumps were checked and the pressure is fine. The problem occurs with both tanks. I also replaced the fuel filter on general principal.
Any insights into where to start looking, which sensor maybe or it's wiring, would be greatly appreciated. Any helpful ideas at all are appreciated.
Thanks

 

There were no codes? Or they did not tell you what codes they got?

 

They said that the codes they got didn't translate (?) to a specific problem. Both shops said that they weren't sure that the scanners that they were using would work on a truck that old.

 

We need to know what codes you got to move on this. Personally, I suspect a bad ECU. It is very unlikely it is your wiring.

 

I would run diagnostic codes and see what it shows. This may give you some clues about a lot of things. You can use a paper clip instead of the jumper he uses. Also with the 4.9 and manual you will need to have the clutch depressed the ENTIRE time you test it. The Innova OBD 1 reader is handy to have and most here use it. .....You will see an extension available for it that is very handy for the 4.9 and manual to read inside the cab while depressing the clutch. The CEL does not have to be on to have codes.