QuestionI have a 1993 8 cylinder F-150 and it's been behaving oddly for some time now.
The first odd behavior was that the truck would act as if it was getting no gas when you pushed the pedal down. However if you repeatedly went up and down on the pedal real fast it would drive very smoothly as if it was getting steady gas. But then you press down firmly without letting up and it would make a loud clunking noise and die.
This only seemed to happen when it was hot out and I'd been driving for a while. I had it checked a couple times. Once by someone who I think did nothing but charged me. And a second time by some friends with a diagnostic machine they said everything was fine once they replaced all the wiring.
The truck ran fine for a while after that until the same problem resurfaced. The two main things I thought of were a fuel pump problem, or vapor lock. I found out the gas lines does come in very close to the engine/transmission. Someone then told me to change the fuel filter. Which I did.
After that the truck ran very well. It started better and ran alot better. Now a days the problem has changed.
I'll start the truck up and it'll act like it's hitting low points the battery gauge will dive, climb, dive, climb. Eventually it'll level out and stay there. Then while I'm driving normally the first few stops I make is as if the power is leaving the truck I'll hit the brakes it'll be non responsive so I'll have to push them to the floor to stop. It's scared me more than once. It's like trying to stop it once it dies but it's still running.
Then while stopped I'll be pushing the brake down, instead of idling normally it revs itself up. People look at me thinking I'm power braking or something. But the truck is doing it all by itself, it's again hitting high and low points but when it's reving up the truck literally moves from side to side like I was gunning the gas while holding the brake down. It's not always that bad alot of times it's more subtle. Then when I get to a long road I push the pedal down it'll be unresponsive until it finally kicks in and then typically the problem is gone for the rest of the day.
Alot of times while starting it's just grind and grind then right as I let off the starter it'll start. As if pushing forward doesn't start it but letting go does.
My guess is that it could be the fuel pumps (dual tanks) and the fuel guages aren't trustworthy. The battery is new, the alternator works, how good I'm not sure. Maybe it's vapor lock or maybe it's something I saw on your site about Throttle Position Sensor.
The only other things about the truck is that the horn is sunken in and doesn't work. And it screeches horribly when it's wet outside. But the belt is good it's just very very loud when it's wet out.
Well thanks for your time.
Answeri need for you to test a few things before we go on.First i need to know does the brake peddle get hard at times.?need to look at the battery conections all conections pos and neg. comming off the neg there is a ground plug this is very important that you unplug and ck the terminal ends.cause it sounds like the pcm is not getting enough power.let me know good luck
