How to diagnose why F150 runs badly?


Asked by Mar 31, 2015 at 09:36 PM about the 2001 Ford F-150 XL Extended Cab 4WD LB

Question type: Maintenance & Repair

I know nothing about Ford F150's so here I am, asking for help in how to determine why my daughter's 2001 F-150 4wd extended cab 5.4 liter engine starts easily but will not produce enough power to move. The truck ran fine and then suddenly deteriorated terribly. A car repair center found nothing in the computer error codes to indicate any sort of error. My daughter doesn't have a lot of money so it is going to be up to me to determine if the truck is worth fixing or not. If the engine timing chain has skipped a tooth then that's the end of it. However, if it is a coil or something else that I could address, that is another matter altogether. The problem is economics and information. I need help in figuring out how to figure out what's wrong and I need to do it without spending a lot of cash. Suggestions on how I should proceed?

8 Answers


Have you changed the fuel filter?

2 out of 2 people think this is helpful.

Agree,with bidD, check the fuel filter,and then check the fuel pump.


Undo fuel filter,cut key on ,if you see good fuel,then pump is good,if not ,then change fuel pump.


Astoundingly quick response! Thank you very much. Why be suspicious of the fuel filter? Where is it?

2 out of 2 people think this is helpful.

Should be under truck driver side,on frame,sound,s like it is starving for fuel.

1 out of 1 people think this is helpful.

Thank you. I'll crawl under the thing this weekend and verify whether or not fuel is coming out of the filter. One other puzzling symptom: when the gas pedal is depressed the engine runs a little faster but misses and does so without power and, this seems strange to me, the overdrive light on the gear shift blinks on and off.


Arg. It takes a special tool to disconnect the fuel filter. As an alternative, I have a can of starter fluid. If the problem is fuel starvation then would it be possible to spray starter fluid into the truck's air intake to confirm?


Symptoms update: Truck starts easily and idles. While in Park pressing the gas pedal results in the truck engine smoothly turning over faster, easily getting to the top of its safe RPM range which would argue against either timing or an electrical problem. While the truck is running, the Overdrive Off light is blinking on the gear shift. Pressing the button at the end of the gear shift has no effect. Putting the truck in gear results in the truck transitioning from an easy idle to running rough and drastically loosing power, to the point where it does not develop enough power to move it on flat pavement. Spraying starter fluid into the air intake results in the truck running much better, developing enough power to move. The fuel filter is not blocked up. Gas flows through it well, a steady stream that is maybe 1/8 thick and flow is strong. I looked at the gas that came out of the fuel filter and it looks clear, containing no water bubbles or other debris. Looking at the gas gauge indicates that the tank is very low but not empty, a little space between the E line and the needle. Just because I have a gas can available I will throw another 4 gallons into the truck although given the unrestricted flow of fuel out of the filter it would be surprising if that made a difference. I am once again hopeful that someone has good suggestions on what I should try next.

1 out of 1 people think this is helpful.

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