Ford f150 mystery woes -- at wits end please help!


#1

Greetings!



I was hoping for some help with my truck problem.



Make of Truck: 1996 Ford F150; V8 302 Engine; 157,000 miles.



The problem first started 3 months ago. Truck is stalling in the morning. Sputters out and dies when it is warming up occasionally. Other times I pull out of the drive way and get a few hundred feet before it sputters and dies. When it dies if your foot is on the gas the engine gets quiet and the rpm gage drops, even if your foot is fully on the gas. When you let off the gas the truck will return to idle and begin to sputter and die.



After it dies I can turn the engine off and back on within a few seconds and drive it the rest of the day with no problem. It will also stall out on occasion as I drive. No matter how many times I start or stop or how far I go. However, after sitting over night, the problem begins again. Weather has no effect. Just before it stalls out there is a sound from underneath around the exhaust manifold like someone is hitting it with a hammer and then is dies. This occurs every day and I am at my wits end.



I have taken it to several mechanics and they all say nothing is wrong. I have replaced the following parts: air filter; fuel filter; spark plugs; distributor (entire assembly); mass airflow sensor; idle air control valve; fuel pump relay. I have also used premium gas and have used fuel injector cleaner to no avail.



Thanks.


#2

You’ve neglected to tell us whether or not the “check engine” light comes on when the engine stalls, and if it does, what do the trouble codes indicate?

I’d try a new engine temp sensor, since this seems to be, at least partially, temperature related (cold start).

Unless the owner’s manual specifies premium gas, which I doubt, forget it. You’re wasting your money. Premium gas won’t help. There is a mechanical or electrical problem. It has nothing to do with the grade of gasoline you use.


#3

The “check engine” light does not come on.

thanks.


#4

You may have a faulty fuel pressure regulator.


#5

Is it belching smoke at all while doing this? The pressure regulator Roadrunner mentions might be it, but the exhaust ought to be coughing up some black smoke if it’s leaking.


#6

This regulator does have a problem when the spring is not centered and the seat only wears on one side. It can stick open at high vacuum conditions like idle and cause a severe engine shudder. It will usually pass a pressure test. A good way to diagnose the problem is to monitor fuel pump current at the fuse. I’ve used spade connectors that fit in the fuse holder and lamp cord to bring it into a meter in the cab. 4A is normal, if it drops to about 2.5A you will have engine problems. If fuel pump is mounted on the frame, there is a second one in the tank that may not be working.


#7

I’ll theorize that the hammering sound is the fuel mixture burning in the exhaust manifold. If the fuel mixture changed from rich to lean fast enough, it could mix in the exhaust manifold to form a mixture that has the correct ratio to burn. The flame to ignite the (now) proper mixture could travel from the combustion chamber to the exhaust manifold. Of course, just a theory.


#8

There is no black smoke of any
kind from the exhaust…


#9

This is a good tech tip Opera House. Thanks.


#10

Dear hellokit,
If this was the problem, what would the solution be?
And since you seem to be a smart person, what is the solution to my ODD KEYLESS REMOTE PROBLEM posted today at 1:18 ?
Thanks