Rough idle/misfire/ rough acceleration

[USAFguy22]

Today I've had really bad idle problems and what sounds like a cylinder is not firing and/or misfiring. I have a 91' and yesterday took it to a machine car wash ( I know I know...) that had a high pressure underbody sprayer. The rough idle is accompanied by intermittent popping heard from the exhaust. My theory is that one cylinder isn't firing and the built up fuel/air mixture is reigniting in the exhaust causing my problems. What baffles me however is how water might have gotten into where a coil pack is... There's a plate above covering the coils. The only way I can think of is maybe water "bounced" off the angled area above the rear bank.
Is there another perhaps more obvious area that water could be faltering things? It's not throwing any CEL codes at me... Please help!

 

[kookoo4nsx]

Park it in the garage for 2-3 days. If a coil is wet, it will dry itself out.

I always cover my engine when I wash it at home.

 

[angus]

Common problem, worst thing is to let it sit and rust, drive the car gently and see if it dries out, if not then you'll have to remove the coils and dry them.

 

[Doc308]

You can take them out and dry them via blowing compressed air onto them and into each plug recess until completely dry.

 

[pgilliam1]

If/when you take the coil packs out, soak them down with silicone spray. It will be absorbed by the rubber, help to keep it resilient and also help with waterproofing. Make sure it is pure silicone and not a spray that says "silicone included". WalMart has it for $2 a can.

 

[USAFguy22]

I swapped all the plugs and cleaned/siliconed the coil packs. Car has about 54k so it was about due for new plugs. Purrs like a kitten now thanks for the help guys