Ok, after a week of horrible misfiring and hesitation I got around to installing new COPs and in the process found out the 2 rearmost plugs on the passenger side were soaked.

It didn't smell like fuel nor coolant. Just plain water. I'm trying to figure out how it's getting wet so I don't have to waste another 2 hrs doing this again.

1. Air conditioning lines condesating and dripping water in there
2. Recent rainy weather we've been having

I'm thinking it's not #1 because I haven't been using the air conditioning during the winter. If it is #2 is there a common source of leakage during the rain?

This time around I was very liberal with di-electric grease so hopefully if the spark plug holes do get wet again it may prevent the spark to jump around.

note: the Ebay COPs seem to work fine except they don't click into the wiring as smoothly as Motorcraft.

 

Find the source of water.
Dielectric grease is not a crutch.
No moisture in the plug wells at all.
The boots can swell at there ends and the grease does not last very long in the form you put it in.
Grease is more a lube for ease of the boots slipping onto the plugs since you can't see it or work on that point.
The grease does have insulating properties but not that much.

 

Thanks

But is there a common source of where the water comes from? Bad weather stripping or just poor engineering?

 

Decided to be proactive and hunt for the leak today by spraying the windshield with water and letting it run down over the cowl. Damn thing seems to leak right over the last 2 cylinders on the passenger side and I'm not even using high pressure. Basically washing the truck could get the coils/plugs wet.

I'll be applying lots of silicone under the hood tomorrow since there's rain in the forecast tomorrow evening. Those of you who're experiencing misfires during rainy weather, you'll definately want to do this, and be suprised at how much water is let through.