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Tim The Ford Tech
Tim The Ford Tech, Ford Technician
Category: Ford
Satisfied Customers: 188
Experience:  Senior Master Ford Tech with 10 Years of Professional Ford Experience.
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1997 Ford F-150: changed plugs..misfire..Truck still misses..coil pack

Customer Question

I have a 1997 Ford F-150 4.6, have changed plugs/wires multiple times, re-gapped plugs had a "mechanic" plug into diagnostic computer with no misfire or codes. Truck still misses occasionally. Could this be coil pack problem? If so why would it not show up on computer check?
Submitted: 7 years ago.
Category: Ford
Expert:  Tim The Ford Tech replied 7 years ago.

It could be a coil problem. Its a good idea to put quality wires on this engine. It is also important to use motor craft or autolite plugs. I've had other brands cause a rough running engine. The misfire moniter in the computer only sets a code after so many misfires. Its likely on yours that that engine hasn't missed enough to set a code. The diagnostic computer the ford dealer has can show which cylender has been missing befor the code sets and can watch a live graph of all the cylenders while the engine is running. They would be more likely to pinpoint your problem.


If this helps you out please accept the answer. Any more questions just ask.



Customer: replied 7 years ago.
The one thing that has me puzzled is that it is NOT a consistent miss in the engine. Maybe 30 seconds of perfect running then maybe 2 misses in the next minute. Seems to run good at road speed????
Expert:  Tim The Ford Tech replied 7 years ago.
So it just has a skip at idle? When it misses Is it a dead cylinder or does the idle just get a little rough?
Customer: replied 7 years ago.

Resembles a wet plug wire on an older vehicle. Not quite as severe as a completley dead cylinder. No backfiring.

Expert:  Tim The Ford Tech replied 7 years ago.

Does it just do it at idle? Did you put Bosch spark plugs in it?