2001 Ford F-150 Has a jerk to it while driving

Tiny
ROSEN
  • MEMBER
  • 2001 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
My f150 started getting a jerk to it while driving, it seems like it mainly happens when im in the 45mph to 55mph range. I have been hoping that the check engine light would come on but it has not.
Monday, December 21st, 2009 AT 9:35 AM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,772 POSTS
THis is a tough one without the check engine light. Because the miss is so temporary, the computer doesn't pick up on it. Has the engine been tuned up reciently? Is it the 5.4L or the 4.6L?

Let me know so I can make some suggestions.

Thanks,

Joe
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Monday, December 21st, 2009 AT 10:43 PM
Tiny
ROSEN
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It is the 4.6L, and it doesnt do it all of the time making it tough. I replaced the spark plugs last week to see if that would help, but that is it as far as a tune-up goes.
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Tuesday, December 22nd, 2009 AT 11:34 AM
Tiny
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Does each cylender have its own coil pack? If not, have you checked the wires? If it does, I have seen the rubber boot that covers the plug actually arc through to the valve cover causing an occational miss. Also, since it only happens at higher speeds, I wonder if the fuel pump may be getting weak and not keeping up. Was the fuel filter replaced reciently?

Let me know.

Joe
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Tuesday, December 22nd, 2009 AT 8:33 PM
Tiny
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It does have a coil pack for each cylinder. The fuel filter was recently replaced. It seems like maybe its when its shifting at that 45 - 50 mph range. So I dont think its the fuel pump.
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Wednesday, December 23rd, 2009 AT 9:09 AM
Tiny
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Please realize that without a check engine light, everything becomes a guessing game. From experience, I have found the rubber boots on the coil packs (that go in the plugs) break down and allow the coil to short through them. It is hard to find because the only evidence is a small light gray spot on the boot itself. The interesting thing is it is more prominent when there is a load on the engine. When you shift at a higher speed, the load changes and demands more from the engine.

At this point, that is a theory, but it's something you could check.

Let me know.
Joe
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Wednesday, December 23rd, 2009 AT 10:26 AM

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