Anyone ever had this problem? I have a 2000 F150 4x4 extcab Lariat with a 5.4L. I was forced to drive through high water yesterday with the sudden 3.5"'s of rain we had in Tulsa yesterday afternoon which resulted in water about 10 inches over the curb and roads resembling rivers. I was doing fine with my truck, but after while I had some hesitation and some rough idle. At first I thought it was water in the engine, but I quickly ruled that out. It's running like an off balanced washing machine on spin cycle. I thought perhaps it was a cylinder misfire. I put my hand over the exhaust and felt extra hard puffs from time to time. I thought maybe water in the catalytic Converter, but ruled that out. So i'm sticking with Misfire.

Anyway, short trip to Autozone this morning to use their code computer. Sure as heck engine shows Misfire on cylinder #3. I'm about due for a Tune Up so I'm going to have it done tommorow. I'm at 99,774 so it's perfect timing on the 100,000 tune up. Do any of you think it could be a coil on the plug on cylinder 3? I thinking maybe water got on the coil and possibly is causing a short. Any thoughts? New coils for the truck are about $120. I'm going to have the spark plugs replaced on all eight, but I'm hesitant about the coils. I don't want to spend an arm an a leg to replace a whole set of coils. I'm thinking it maybe inevitable.

Anyone ever had problems with water getting on the coils on the plugs?

 

I have never personally had this issue but, have seen many threads with this type of problem. These engines do not like water on the COPS, on the plugs or in the plug wells.

Cylinder 3 is the the third one back on the passenger side of the engine. If water splashed up on top of the engine, it could have very easily gotten to this COP. It wouldn't hurt, to pull this COP off, inspect it for cracks in the housing of the COP, signs of water in the plug well, and the plug for a broken insulator.

Good luck!

 

I'd guess its caused by water in the hole with the plug causing the cop to misfire to the head. Its common with these motors. Be sure you replace the boots under the coils along with the plugs. They dry out & crack which will cause misfires.