engine loud and knocks/pings after car wash

My 98 Dakota engine is abnormally loud and it knocks/pings for a few minutes whenever I exit a car wash. The noise dissipates after several minutes. This is just an automated car wash. I'm not lifting the hood and getting the engine wet. I'm wondering if this is a sign of bad things to come.

The water from the car wash will roll from the windshield onto the cowl, engine, ignition wires, fuel injector wires, and cause misfiring.
Action-

1) Lift hood
2) Put a garden hose with a little water pressure on top of your windshield.
3) Watch the water roll
4) Clean all the derbis, and leaves out of the cowl.
5) The water should drain proper without rolling onto your motor.

I was thinking this might be caused somehow by the moisture in the air in the car wash as opposed to the engine getting water on it. I'll give your solution and try. Hopefully that is the problem. Thanks.