'94 NSX - stumbles / rough running - mainly when driven in rain..what could it be?

[Meeyatch1]

Hey gang. So my 1994 NSX with just over 203,281 miles has developed a problem. About a month or so ago my wife drove it to work, and said that when she was driving home in the rain that it was stumbling and did not sound right. Sure enough, she came home and it sounded like it was missing. Just not running right at all. I went out and drove it, and it would stumble and run like crap.

I brought it home, changed out all of the spark plugs with new ones, looked for obvious damage or other faults with the coil packs, and re-assembled the car. I went for a drive, it ran well for a short time, and then back to running like crap.

The car sat for a few days, and I finally drove it again (totally dry day), and the car ran like a champ. No problems at all. It was dry for weeks after that and no issues. She drives it to work yesterday in the rain, and the car does the same thing it did before. So driving in the rain is a constant in the recurrence of this problem.

The fuel filter is maybe 15,000 miles old....but cannot imagine that would be impacted by rain, as it would run like crap all of the time if this was clogged.

Any ideas?

 

[JD Cross]

I had the same problem after driving in the rain and initially assumed it was plugs/coils so did as you did.
The problem remained so I took it to my dealer.
The tech diagnosed it as a failed igniter, replaced it and it's been fine since.
He also suggested putting dielectric grease at the base of the spark plug insulator before putting the cap back on.
He said it would help prevent water, particularly in the rear bank, from working up the plug shaft and causing a misfire.