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Engine intermittent misfiring in mid RPM range

Tiny
MDSMITH1951
  • MEMBER
  • 1994 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 136,000 MILES
I have a 1994 F150 5.8 litre automatic 4x4 with 136.000 miles. It has developed an intermittent engine misfire in the 1100 -1400 rpm range under normal load in higher gears, mainly after engine warm up. I have replaced plugs, wires, distributor cap, rotor, injector service, fuel filter. Miss seems to go away at highway speeds or I am unable to detect. What's next?

Mike
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Wednesday, September 22nd, 2010 AT 8:28 AM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Mike:
Have you checked fuel pump pressure?
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Wednesday, September 22nd, 2010 AT 1:20 PM
Tiny
MDSMITH1951
  • MEMBER
  • 1 POST
No I haven't. The fuel filter was very dirty when changed but that didn't seem to make a difference. I will see about getting the pressure checked. Is there anything else I can have checked at the same time to rule out other possible causes?

Thanks for your help,
Mike
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Thursday, September 23rd, 2010 AT 8:08 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Check the catalytic converter for possible plugging.

Let me know what you find.

Joe
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Saturday, September 25th, 2010 AT 12:32 AM

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