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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 36024
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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Ford F150 Pickup PROBLEMS My 1998 Ford F150 truck (V8 4.6L,

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My 1998 Ford F150 truck (V8 4.6L, manual trans, 125K miles) lacks power, accelerates slowly, barely maintains 65 mph with pedal-to-the-floor throttle and got <8 mpg on a recent 400 mile interstate-highway trip last weekend. No engine lights or dashboard codes.

I checked fuel pressure today. 30 psig at idle, varies between 30 psig (coasting) and 38 psig (under acceleration) while driving.

Truck has been off the road for 2 years until last weekend. Last weekend, I charged the dead battery, started the truck and took a test drive. Full power, strong acceleration and normal operation. Whoopee! Then I pulled all fuses one-by-one (under hood and under dash fuses) to search for a key-off battery drain. Found the battery drain circuit (dome light circuit). Took a second test drive and the PROBLEMS appeared (see above). I then drove the truck 400 miles using several tanks of gas. Added LUCAS injector cleaner to each tank of gas. Still lacks power, very slow acceleration. Shimmers slightly under hard acceleration ... exactly as if the fuel pump were failing.

What's wrong? What's the next step? I am an experienced DIY'er.
Hello and Welcome to Justanswer,

My name is XXXXX XXXXX I am here to try and assist your with your question.

Providing your fuel pressure is ok , I would start with removing the negative battery cable for about 10 minutes to reset the PCM and fuel trim. If the problem still there then try loosing the exhaust till you have a healthy leak and drive it and see if the power has returned, if so suspect the cats are restricted.
Customer: replied 6 years ago.
Thanks, Ron. I will follow your advice.

A follow-up question ... would a restricted cat cause a hotter-than-normal cat? The reason I ask is because I noticed an unusually-warm passenger-side floor board (directly above the cat) last weekend when I drove 400 miles. I thought the hotter-than-normal floor board was unusual, but I did not connect it with the loss of power.
Yes it very like could and would, another thing that would as well is if the system is over fueling on that bank but if that was the cases you would usually get a fault code.
Customer: replied 6 years ago.

Resetting the PCM and fuel trim fixed the problem. I just burned rubber around my neighborhood after disconnecting the battery for 10 minutes. Truck has full power again.

Good job, thanks. I'll accept your answer.

I have another new question ... is there a way for me to select you after I accept the answer to this question?

Great work!!!! All you have to do is to get me again is place my name in the question. I will get it for you. Thank you as well.
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