06 5.4 engine issues

[mike nadeau]

Engine seems to run fine. I have noticed a couple of times at heavy acceleration I will get a couple of misses. Any ideas? I was thinking a COP on the verge but dont know. Plugs only have about 38k.

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[mike nadeau]

So I guess no ideas?

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[bedrck46]

you say the plugs only have 38k on them How many miles on the COP's and on the connecting boots/wire
I once had a problem with a miss on a 5.4 and it turned out to be the boot that connects the cop to the plug You could pull the cop's and check them with an ohm meter and the boots would cost about 40.00 to replace If the Cop's check out ok and your plugs are ok I would replace the boots

 

[Stoned06]

Missing under heavy acceleration points to a misfire due to a bad COP or plug. It seems you narrowed it down to a COP, but just get the codes read if the CEL light was flashing. If not, then I would suggest replacing the COPs all together.

 

[CWOLAW]

Had the same issue on my 1998 5.4 - 140K miles. Replaced the plugs at about 130K (originals) and replaced the boots on each of the COP's too, but not the COP's at that time. Mistake Number 1! Should have replaced them when I was in there the first time. It did seem to run a little better, but when towing the boat (under load), misfire was bad, even after plug change! Then, noticed the same bucking to a much lesser degree, when not towing the boat, but going up hill (under load again). I never got a CEL though! Just replaced all the COP's and Boots yesterday. Runs much better now! Couldn't get it buck once, although I have haven't towed the boat yet (and won't until spring) to see if that resolved the problem completely. However, I did notice, that the #3 Boot was discolored (Tan) - completely, not in just one place. These have less than 10K miles on them. Couldn't find any holes. Any ideas on what may have caused the discoloration on only that one boot? Bad COP??