This is a 1997 F150 Flareside 4x4 with a 5.4 that has around 300k on it. It has recently started running rough after a rain and takes several days to straighten up. A diagnostic of the problem showed an issue with #1,2, &5 coil packs. This is my 17 yr old son's truck, and he tried to dry out the connections from the wiring to those coil packs, and he also put some dielectric grease in the connections to keep water out. But after the last rain he is still having a problem with #5. Do you guys know of anything else that can be getting wet that we need to check. Or do you suspect that the grease is not keeping the water out, and that it is still getting wet? He took it off again and tried to make sure it was dry, but it is still skipping. Any ideas of things to check or ways to better protect this area from the moisture would be much appreciated.

Thanks in advance for your help.

 

My 17 yr old son would be very thankful for your help on this issue. I have been working a lot lately and he has been working on this issue pretty much by himself with the help of his grandfather who is pretty mechanically inclined, but they have had a hard time getting this resolved. He is going to buy a coil pack today and replace #5 although I have my doubts that will fix it, since it only seems to do it after a rain. Your expertise and opinions would be appreciated.

 

If it was a rear coil, I'd say to check the rear seal where the hood meets the cowl. I still might check that and repair if needed. Check the connectors hooking up to the coils. I suspect replacing the #5 coil will help. The boots and wires can be suspect and should be checked, but it's possible the coil is damaged and is sensitive to the moisture in the air. Basically, my rule of thumb is that if cleaning up the boot/wire doesn't work, replace the coil. I know that's not a ton of help, but you're on the right path.......

 

Number 5 is the front cylinder on the drivers side, you mentoin he dried out the connector to the C.O.P. but don't mention removing the C.O.P. It could be water got under the rubber seal (boot) on the C.O.P. The boots are sold seperate from the cop if you find yours is in bad shape, and of course it could be the coil ( C.O.P) itself is worn out, easy to change.
Good luck

 

My son is out of school and he and his grandfather took a look at it again. Turns out that your advice was dead on. He originally thought it was the conn to the coil pack getting wet and he dried and added dielectric grease to keep moisture out of the conn. But this time he removed the coil pack and found water under it and around the spark plug, no doubt causing it to faul out. He dried it up real well and tried to seal it up around where the coil pack goes in. It is running like a new one for now. If it gets wet again you recommend changing out the boot? I thought it was all one piece, but from what I read in your post you can change out the boot and don't have to buy the whole coil pack?? Thanks again for your help, you made a 17 yr old very happy today by being able to get his truck running smooth again.

 

Glad I could help, from your description it sound like the boot is worn out. Might just be a waste of a few bucks and minutes but yes I'd swap the boot out.