my nephew has an 87 150 4x4 fuel injected 302 auto, it starts good, runs smooth at idle, accelerates good in nutral, but when driving has slight stumble at steady speeds, but accelerating from stops it chopps hard and feels really jerky, get worse as motor warms up. i'm thinking fuel pump but would like to hear any other suggestions. we already changed filter, and throttle position sensor.

 

Are there two tanks on this truck? If so, does the problem happen on both tanks? I also think there is a second filter before the high pressure pump, has that been checked or replaced too?

How old are the plugs, wires, cap and rotor? Is the Check Engine Light On? Have you checked for any codes?

 

only one tank, don't see a filter from tank to pump, plugs and wires cap and rotor were replaced about 3-4 months ago, light is on but don't have scanner.

 

No scanner required: Ford Fuel Injection How To Run a Self-Test

I am not that familiar with the vintage truck you have. I know there is an in tank pump then a frame mounted high pressure pump. Many trucks of your vintage have a reservoir/filter before the high pressure pump. With only one tank you may not have one.

Check the codes using the procedure above, bring the engine/transmission up to temperature before running the tests/code check otherwise you may get false errors related to temperature out of range. You are only interested in the KOEO tests and Continuous Memory read out at this point.

It might be wise to invest in a fuel pressure gauge/tester or rent one from da' Zone or other parts house.

 

i'll give it a shot thanks, let you know what i come up with