I am having trouble with my truck. I have a 96' F-150 with the 302 V8. Has the 5 speed. It has 89,900 miles and has run perfectly until now. The problem started Monday without any warning. The engine can be started (most of the time) and will idle almost perfectly. But when the throttle is depressed the truck will either die or sputter at idle speed. Even when the throttle is floored the engine will sputter and run somewhat, but will only run around 800 rpm. I can hardly even move it in the driveway. No backfiring (so I din't think it's ignition related).
I have narrowed it down (I think) to a fuel delivery problem. If I shoot carb cleaner into the intake it will speed up and run when the throttle is depressed.
Fuel pressure at the schrader valve on the fuel rail is about 40 psi Key on-engine off. With the engine running the pressure at idle is about 30 psi. When I goose the gas the fuel pressure goes up somewhat, but the engine still cuts back to idle or dies.
So far I have checked the throttle position sensor (fine) and I have disconnected the exhaust. It runs better but still will not take throttle. Everyone says it sounds like the exhaust is plugged. But disconnecting it at the manifolds really didn't help much, although it sounded great.
When I disconnect the vacuum hose at the fuel pressure regulator the fuel pressure increases as it should but the engine will not take throttle.
The problem started all at once. Ran fine until I started it and pulled out the driveway and then it wouldn't accelerate. Barely got it back home (about 1/8 mile).
I also drained some fuel into a glass jar. No signs of water. Plugs, wires, cap, and rotor replaced at 50,000. New oxygen sensors installed about 20,000 miles ago. New fuel filter Tuesday (when I started having problems). Still no change.
Truck has been taken care of, burns no oil.
Oh...and no check engine light.
Any help is surely appreciated. I don't know where to look next....

 

You need to hook it up to a scan tool and check the data stream. That will show you right away.

 

I agree you might need a scan tool for this one. Check the MAP sensor first though, if that specs out ok you will need to look at the scan data to make sure the computer is recieving all the proper info from the sensors. There could be a broken wire so even though the sensors send the info out, the ecu never recieves it.

If it started without warning i don't think it will be anything like bad gas, injectors, dirty tb, etc. Sounds like a fuel problem caused by an electrical problem.

-Jon

 

Thanks for the replies. I finally gave in and decided to send it to the shop. Wrecker picked it up yesterday. First time in the shop. Can't complain about almost 90,000 toruble-free miles I guess. Will post results.

 

Well, I talked to my mechanic today and the results of the scan are:
Computer shot
Pickup coil in distributor not 100 percent
Mass airflow sensor out of range

There goes my Christmas bonus. Happy New Year.

 

Sounds like you have my luck, maybe this dancing banana will make you feel better

 

Thanks! It turns out that the computer was not quite as high as I expected. It was $50 for a used one plus shipping. 90 day warranty. I think new was around $300. UPS should get it here on Monday. The computer was not easy to find with a code that matched mine. Maybe because 96' was a short year? Maybe it'll be back on the road next week.

 

Finding a computer with Mass-Air would be bit more challenging since I beleive it started in some 95's.