My truck is back in the shop for the 2nd time now. The engine runs very rough whenever it rains. The code points to #6 igniter. We had it replaced about 2 months ago and all was fine until the rain came. Everything is fine when the roads are dry. My mechanic is somewhat stumped.

Any ideas would be greatly appreciated.

 

Well, rain means moisture. Moisture is a problem whenever you have a cracked COP(ignitor). Moisture gets in there and disrupts the the electronics of it all.
Your mechanic should be able to read the resistance of the coil pack and compare it to the others. If it measures high, I'd say you need a nee one which would mean that the one you replaced is still under warranty.

 

Thanks for the reply, Dirtydog. I just got off the phone with my mechanic. He said he'd already replaced the coil pack twice (I didn't realize that). Could it be water is seeping down through the windshield, like a broken seal?