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It runs really bad

Tiny
ANDREW VARGAS
  • MEMBER
  • 1999 FORD EXPEDITION
  • 5.4L
  • 2WD
  • AUTOMATIC
  • 270,000 MILES
My SUV quit running on me in the middle of the road last week. My mechanic said it was the fuel pump, so we change the fuel pump and now it runs really bad. I changed the boots and spark plugs because he said probably that and it still runs bad. Please help and no code comes up.
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Sunday, June 11th, 2017 AT 1:12 PM

11 Replies

Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Have you changed the fuel filter? If not, do so, and make sure that none of the lines coming from the tank are kinked or anything.

https://www.2carpros.com/articles/how-to-change-a-fuel-filter

The filter in your truck should be under the car, on the driver's side, attached to a frame rail.

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Sunday, June 11th, 2017 AT 1:30 PM
Tiny
ANDREW VARGAS
  • MEMBER
  • 7 POSTS
I did.
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Sunday, June 11th, 2017 AT 1:31 PM
Tiny
ANDREW VARGAS
  • MEMBER
  • 7 POSTS
It is weird because once we put the tank back on and cranked it up it was running fine, but it is raining really really bad so I am not sure if it has something to do with the rain and the next day was running bad.
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Sunday, June 11th, 2017 AT 1:34 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Well there could be a lot of things going on that cause this. Without any codes diagnosis won't be easy. I'd start with checking that fuel pump. If it's an aftermarket pump (like most of what you get at the auto parts shops) then it could be faulty out of the box. I've seen that happen myself, so it wouldn't surprise me. Get the fuel pressure checked following this guide: https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator. Let us know.
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Sunday, June 11th, 2017 AT 6:40 PM
Tiny
ANDREW VARGAS
  • MEMBER
  • 7 POSTS
Pressure is good. Could it be a bad fuel injecter
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Sunday, June 11th, 2017 AT 6:43 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Possibly. But on most V8's one bad injector would not make the engine run so terribly like you describe. Yes, you would notice a misfire and maybe even some hesitation, but it would keep running in a decently reliable manner. Out of curiosity, what is the pressure reading? Should be between 242-310 Kpa (30 to 45 PSI) with the key on and engine off or between 193-310 Kpa (28 to 45 PSI)with the engine idling.
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Sunday, June 11th, 2017 AT 7:09 PM
Tiny
ANDREW VARGAS
  • MEMBER
  • 7 POSTS
Pressure is fine I have had three different people test it.
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Sunday, June 11th, 2017 AT 7:12 PM
Tiny
ANDREW VARGAS
  • MEMBER
  • 7 POSTS
Yes decently. When I push the gas it is rough until it hits like 10 to 15 mph then stops until about 45 mph it start running rough again.
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Sunday, June 11th, 2017 AT 7:15 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Okay, I would start with checking the fuel pressure regulator then. Again refer to this article. https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator. Let us know.
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Sunday, June 11th, 2017 AT 7:17 PM
Tiny
ANDREW VARGAS
  • MEMBER
  • 7 POSTS
Will do.
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Sunday, June 11th, 2017 AT 7:17 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
Please let us know what you find.

Cheers, Ken
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Wednesday, June 14th, 2017 AT 10:32 AM

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