Because of gas prices, I tend to let my Ex sit without driveing more than I should. Normaly I will dirve it about once every 2 weeks and have no issues. We had a TERRIBLE wind/rain storm the other day and for the first time ever, the truck is running very rough. The ses light has not come on but there is a definet miss. I drove it around some yesterday and it didnt seem to get better, but today it seems to be intermitantly clearing itself up. When it is doing it the exaust even sounds differnt. Today you can actually hear the differnce at idle when it starts to misfire.

While I know I should probably start thowing money at it, I am wondering if it is just from sitting and will clear itself up once it dries up?

Wishful thinking?

2001 V10 4x4 Excursion

 

Here is video of the change in sound.

Thoughts?

YouTube - Truck miss

In real life it does not sound as much like a knock, more like a louder puff, puff, puff....

 

You probably need to pull the COPs and either dry out the holes, or replace the boots.

Use dielectric grease around the tip of the boot where it seals to the plug, around the top of the boot where it seals to the COP itself, AND around the seal area where the boot seals to the head.

Once water gets down there, it's VERY hard to get rid of without pulling everything apart.

The water turns to vapor when the engine gets hot enough, and won't escape. Which basically shorts across the coil. Then when the engine cools off, the water condenses on everything, continuing to short out the coil. Process repeats. It never goes away. Been there, done that with my 4.6L's with coil packs and plug wires. Same principal for the V10 with COPs though. The water never EVER gets out.