2003 4.0 SOHC misfire after car wash?!

[phillip723]

okay, 2003 Explorer XLT 4.0 SOHC. Truck sometimes would misfire when started cold in the morning after sitting overnight. Always stopped with throttle and when warmed up. Just one cylinder, occasionally would set CEL and always P0306 and P0316. Kind of forgot about it because it hasn’t been doing it as much as the weather warms up. Lots of rain the past few weeks and it still hasn’t done it.

Today it was starting to get nice and I took the explorer through an automatic car wash, including the undercarriage wash where it sprays a lot of water up from underneath. Truck drove in fine, and once I came to the stopping point I put in park and shut it down. Upon start up it immediately began missing. Harder than usual. By that I mean it felt worse and it took more throttle and driving around for it to stop completely. I opened the hood while it was missing and noticed a lot of water under there. I’m thinking the plug wires got wet and shorted? Maybe that would explain the occasional cold misfire in the mornings too, like maybe some dew on the wires? Any help appreciated, when I get a chance soon I’ll try the water spray on the wires test and see what happens. Just wondering if anyone has experienced something similar with theirs. Any help appreciated.

 

[mountaineer2004]

I had the same problem. Water leaks down onto engine, from wiper cowl attachment points.
Stupid design by Ford. Use silicone, below attachment points, to stop leaks. You're problem will go away (hopefully).

 

[shucker1]

If the spark plug sits inside a well in the cylinder head my guess is that one of the wells got full or water.

Pull the spark plug wire out of the well and blow the well clear with compressed air.

Same thing happened to my 2011 Fusion with Inline 4 after I got too aggressive cleaning the engine bay.