Mechanics

PLEASE HELP

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?
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Bwonder68
October 17, 2013.



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

Roy

ASEMaster6371
Oct 17, 2013.
Didn't change plugs but compression test was done and compression is good

Tiny
Bwonder68
Oct 17, 2013.
I would replace the plugs before replacing any coils or injectors.

What was the compression?

Roy

ASEMaster6371
Oct 17, 2013.
I don't remember the number but it was fine. Why change the plugs first?

Tiny
Bwonder68
Oct 17, 2013.
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.

Madmike1735
Oct 19, 2013.