[metrocube]

It could be from moisture.

Clean the coil packs and spark plug boots.
Apply dielectric grease around the coil packs and inside the boot.
Reinsert the coil packs into the engine.

for other possible coil pack and plug related problems, see http://www.lotustalk.com/forums/f25/coil-pack-arcing-77822/

 

[Bryker7]

Mine were like that and actually caused slight miss fire, the grease worked but water still got down the tubes, so I sealed the top of the coil packs and its been good now. This was only a problem on the 2 passenger side plugs

 

[Gunpilot]

They all do that. Water runs down inside. Get liberal with the dielectric grease and you can silicone the top of the coil pack. It's not mud, it's rust.

 

[fgthwar]

thanks. i'll give them all a good scrubbin and dieletric greasin. Probably best done with a new set of coils, since it has an ever-so-slight rough idle. I'll update after.