Toward the end of a 100 mile trip the engine in our 1995 E320 began running rough when the car was stopped. Pulled the spark plugs and the plug in Cylinder 1 was wet and the top of the piston looked wet also. The rest of the spark plugs appeared normal and the top of the those pistons were dry. Replaced the spark plugs and the problem still exists. It seems like the ignition wire to Cylinder 1 has gone bad and the spark plug is not firing. In the past I've had one of the 3 coil packs suddenly go bad, but in this case the engine does not run as rough as with one bad coil pack. What's the likelihood of the ignition wire that runs from the coil pack atop Cylinder 6 to Cylinder 1 suddenly going bad while driving? Any other ideas as to the cause of this problem?

__________________
Fred Hoelzle