1999 FORD F-150 PLEASE HELP

  • Tiny
  • bwonder68
  • 1999 Ford F-150
  • 164,000 miles

I have a Ford f150 5.4 liter and the check engine light came on. It runs horrible and idles rough. Diagnostic done and it said it was possible that it was a ma's fire on cylinder 3, or insufficient air flow. Replaced injector and coil pack. Replaced o2 sensors. What could be wrong?

Thursday, October 17th, 2013 AT 6:11 PM

5 Answers

  • Tiny
  • ASEMaster6371
  • Expert
  • 25,555 posts

Start with a compression tes. Did you change the plugs?

Roy

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Thursday, October 17th, 2013 AT 6:14 PM
  • Tiny
  • bwonder68
  • Member

Didn't change plugs but compression test was done and compression is good

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Thursday, October 17th, 2013 AT 6:17 PM
  • Tiny
  • ASEMaster6371
  • Expert
  • 25,555 posts

I would replace the plugs before replacing any coils or injectors.

What was the compression?

Roy

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Thursday, October 17th, 2013 AT 6:22 PM
  • Tiny
  • bwonder68
  • Member

I don't remember the number but it was fine. Why change the plugs first?

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Thursday, October 17th, 2013 AT 7:07 PM
  • Tiny
  • madmike1735
  • Expert
  • 964 posts

What were the codes retrieved? A cyl 3 misfire would set a p0303. Insufficient air flow is a whole different issue. If u already replaced the coil, and verified compression is good, then try swapping the spark plug to another cylinder, clear the code, and see if the misfire moves to that cylinder. Process of elimination.

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Saturday, October 19th, 2013 AT 9:21 PM

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