i recently bought a 1997 f150 5.4 4X4 Lariat, 204K. I finally got it to sustain an idle, buts def got a miss to it. OK, plug job. i go to pull the coil packs and find that there pretty nasty and two had water in the plug sockets. i know this is not good and would prob affect firing of the spark plug, but would it cause damage to the coil pack itself? is there a way to test a coil pack with a certain combination of meters? the pack appear to original equip. motorcraft, and the plugs are motorcraft platinums. the spark plugs (according to the sticker under the hood) are supposed to be gapped at .054-.056, but im measuring about .076 because part of the electode arm is visibly worn off. im hoping the coil packs are ok and the spark plugs are just shot... what sat you? THANKS!!

 

Put new plugs and boots in if there is that much errosion.
Find out why there is moisture in the plug well/s.
After this work, pay attention for a stumble in OD and light throttle.
If you feel this, then a coil/s are fauty.
No, you can't meter coils for the above fault. It would not be a 'hard' fault that would set a code.
A 'hard' coil fault will be a permant miss and set a code you can see what cylinder it is.
Good luck.

 

Yup, change the plugs and set them at .054". Testing the older tower style packs was easy with a multimeter, with the COPS however, I don't think it is possible. Do an OBDII scan on it and see if it misfires. If so, change the coil pack to another cylinder and see if the code follows. BTW yes, water in the tubes can easily destroy a coil pack.

 

ok, i finally got all the spark plugs out. on the passenger side, the plug closest to the radiator was the killer. the gap between the arm and the elec. tip was bridged by a black and gritty substance. all the other plugs appeared to be worn (rather extensively), but nothing out of the ordinary. is this caused by worn valve seals or what? could the c.o.p. have went bad and then the plug gap been bridged?

 

You can't tell much of the time what caused what until you replace the parts, then run for some time to see what developes and a check of that cylinder's plug condition.
An oily accumulation is usually oil from worn intake valve stem seals or even bad rings.
A dry fluff is usually largely unburnt fuel from a plug condition.
A hard missfire is a plug, boot or coil or any combination that would set a code.
A light missfire can be the coil, boot pin hole, a plug gap bridge contamination etc.
It's hard to predict until you do the service and see what the future brings on an old motor.