i have a 98 f150 4 x 4, 5.4l engine, 150,000 miles.
driving home the other day it stalled on me all of a sudden without warning.
it had been running fine. a few days ago something came loose in the exhaust and has been pretty loud lately. also i can hear the fuel pump come
on when i turn the key but it runs only for a quick second ( i don't know how
long it should stay on at startup) i can fire up the truck but it quits immediatly. if i hold the gas all the way to the floor i can barely keep it
running but very rough. not enough to even try to move it any where.

 

Welcome to the forum!

The rough idle sounds like a stuck Idle Air Control (IAC) valve. There have been a number of posts about it. Some clean them while others replace it.

 

buy a fuel pressure gauge and see if it is within spec, 40 psi i think. if low i would go new pump and filter. Also when checking it see if it holds the fuel pressure, if it bleeds down rather quickly you may want to replace the fuel pressure regulator too.

 

Jammed up fuel filter. When did you change it last? Welcome to FTE.

 

what if the cats come apart and pluged up the exhuast or a baffle in the muffler is lose and when start it it closes the exhaust off but iam not sure good luck

 

This is the most likely cause.

 

A rough or low idle is classic IAC, but if you hold the pedal down a little it would run fine. If you hold the pedal down a little and start it will it run OK? If so I say IAC, if not something else is wrong. You say all was well before you heard an exhaust problem. Find the source of the exhaust leak and look in that area. Maybe somethimg plugged as others mentioned. Maybe a wire for one of the upstream O2 sensors is cut. As far as the fuel pump noise, that is standard on startup. Listen to most any other fuel injected vehicle, you will hear the same thing when you turn the key to run position. If it runs that bad it should toss a CEL, then you can pull codes. Good Luck, try to let us know what you find.

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