Rain, misfires & coil death

[DavidEBSmith]

So today we got caught in a deluge with the Mountaineer (V8) and once again, getting misfires on the #8 cylinder. Although I can't see any water on the engine, I'm sure I'll find some in the spark plug hole once I pull the coil.

This is the second time recently this has happened (and once on the #4 cylinder) and in the past I've just dried out the spark plug hole and replaced the misfiring coil to fix the problem. Today's question is, when water gets in the spark plug hole, which presumably allows the spark to leak to ground instead of going through the spark plug, and thus causes the misfire, does this actually damage or kill the coil? Or is there water getting into the coil somehow and causing a short? If so, could it be resuscitated by letting it dry out? What exactly is failing here?

 

[Explorer_PL]

If you search, you'll see that some users (including me) designed a gutter under the windshield under the hood.
I just used a piece of aluminum trim from Home depot, other were more sophisticated.
The water never killed the coil in my case.
That fixed my issue.

 

[Parked@Dunkin]

Here in San Antonio, we've gotten heavy rains from what's left of Patricia. I had trouble with misfiring last spring when I drove through a puddle I couldn't see very early one morning, took it to mechanic who dried and replaced coils.Yesterday, I was driving, saw a good sized amount of water in my lane (SA is notoriously bad for water drainage) and slowed down. Even so, I could hear/feel a good amount of water splashing up into the engine compartment.

Sure enough, the check engine light came on and she was rough in idle. While trying to get her home, check engine would go from solid to blinking then back to solid periodically (20 minutes of driving) but no shutters, just idle rough. I've let her sit overnight and am taking her to Autozone for a quick readout. If nothing major shows up after testing, plan to let her just dry out.
Should I let her just dry out by sitting there? Remove coils? Continue to drive?

 

[Parked@Dunkin]

testing said #3 . she still idles a little rough but no problems getting her up to a high speed (45+). came home and removed coil on #3 . old coil came out dripping with water. disconnected battery, rolled up paper towel and lowered paper towel into #3 , got about 1" in and paper towel is soaked. advise on how to remove water ?

 

[NickSantagataa]

testing said #3 . she still idles a little rough but no problems getting her up to a high speed (45+). came home and removed coil on #3 . old coil came out dripping with water. disconnected battery, rolled up paper towel and lowered paper towel into #3 , got about 1" in and paper towel is soaked. advise on how to remove water ?

air hose , shop vac with a tiny nossle , crank the car ?

 

[pjw73nh]

Two and half years ago at about 75k miles, I chased various misfires up and down both sides of the engine for months. A Ford tech/friend of mine talked me into (and I mean really leaned on me hard) to change the plugs (realizing some might break (see TSB)) and also change all coils to Accels. I took his advice and up until today, I have not had one misfire (102k miles). Today, I chased down bad coil. Swapped it with a new one, all is well. I am considering that an oddity. If more of them start going bad, I'll revise my opinion. I can't urge you enough to just bite the bullet and change the plugs and coils and be done with it.