Lots of rain lately and I'm getting a constant misfire. Ran the code and it's #4, pulled the plug wire and found moisture on the bottom of the plug boot. Question--how can water get in there? Only from the top? Or is there a drain hole, too? Gooped some dielectric grease on the sides on the boot thinking that would seal out the water, didn't help.

I can dry it off and it'll run good, until I splash thru the next puddle!

Need some fresh ideas, thanks. BTW, it's a 1998 4.6

 

It's most likely coolant leaking from your heater core lines. Is there any kind of puddle under the truck where it's parked ?

Yea those lines above #4 leak under pressure. Look for evidence, - the top of the starter usually gets covered with coolant as well.

 

Yep about a 95% chance thats the problem with #4. I put two clamps on mine even though it didn't appear to be leaking. Solved the problem.

 

It doesn't appear to be leaking, nor can I smell the anti-freeze. I'll 2 clamp them this weekend. Looking at the plug boot design you would think it wouldn't allow water (or coolant) to pass. Guess that's a problem with these deep recessed plugs.

My little Honda MX bike has an itty bity drain hole that runs from the spark plug well out to the side of the head and when it clogs up the same thing will happen, except it's a single cylinder so it's a no go situation.

Thanks