We got 15 inches of rain here on Friday. Had to drive (very slowly) thru some fairly deep water, but with an 8" lift and 38" tires, the water never got higher than my nerf bars. It's a 2000 5.4L ~~ 65k miles. Started running rough that afternoon. Obviously something got wet, but I have a hard time believing that I got water in the coil packs / plugs. It's done this in the past after I was in some deep water, and it self corrected after a couple days, but I'm now on day 3 and it's not much better (although I have not driven much in the past 3 days). As a precautionary measure I changed the oil & tranny fluid. Any ideas and is this anything I should be concerned about. Thanks for any suggestions.

<edit> and by running rough, it's most noticable at 1500 & 2000 rpms....if I keep the rpms at those levels, the truck starts lurching. If I give it gas and take it to a higher rpm, it's ok, although sometimes there is a slight hesitation. The rpms jump a little at idle too. Thanks again.

 

i saw the same thing on a ford mustang..... turned out to be from a crappy homemade air intake from the previous owner.... anyhow, water got sucked up to the intake, and the MAF went all haywire. i would check yours, maybe clean it, and make sure it is totally dry. but, it could be to late and just need changing.

 

It probably is the coils. How old is your truck?

 

UPDATE: misfire in cylinder 7

It's a 2000. Guess I'll start taking stuff apart this afternoon. I was really hoping it wasn't plug/coil pack related.....they don't look like much fun to get to. Just did a search on here and it doesn't sound like it will be *that* bad to replace 1 plug. Had all the plugs replaced 2 yrs ago, so the rest should be good.

Any ideas why moisture would get to that plug/coil? Maybe the boot went bad?

Also, how do I tell if the coil pack went bad?

 

what engine do you have, v-8, or v-10? it is possible that you could have a bad boot under the coil. if you have the v-10 then it shouldnt be too bad, since cyl 7 is towards the front of the engine. but #7 on the 5.4 is under the fuel rail, making it more difficult. there are threads on this site with how to test the coil, but i dont think it is very reliable..... since the resistances in them change as they warm up.... thats one reason why they usally tend to show the "shutter" when they are going bad, but only when warm. plus, i checked mine with their methods, and it measured the same as the rest, but i changed my bad one anyways, and no problem since. goodluck !!

 

thanks for the help guys --- got fixed last night. Pulled the coil pack (boot had moisture on it), took it up to Discount Auto and had it tested -- it was bad. Replaced coil pack, boot, and plug, and it runs like a champ. Really wasn't as bad as I was expecting. I'd just love to know how it get wet in the first place.

 

I began to have that problem on my 2000 V10. Funny that it did not occur until the truck was almost 5 years old. After a heavy rain, I had heavy missing. On a warm sunny day, I pulled the COP boots and filled them with dielectric grease. No problems since. It has been about 6 months ago and we have had lots of rain since then.

 

Big Red,
You never know which way water will splash, especially when driving over uneven surfaces and such. It just takes a little to get sloshed up on top of the engine. The plug cavity is like an unsealed chamber that just a little warmer than its outer components. When moisture comes in contact with the lower part of the COP, and if that area is not sealed, the moisture gets "sucked" (for the lack of a better word) into the plug cavity, where it then can, and mostly does, get hot enough to turn to steam. It them wicks up inside the plug boot. If the boot has any sort of crack or hole in it the voltage will creep out and ground against the plug cavity, causing the COP to fail or weaken.

Sealing the COP/cavity area with di-electric grease will help. Also seal the area where the boot attaches to the COP with the same grease.