I've noticed this issue recently. A couple of weeks ago I had to drive through a puddle of water about half a foot deep and 20 feet long. Then after 20 minutes I noticed RPM begin to studder. Gas pedal felt a lot less responsive, but after I floored it, there was full acceleration and the studdering was gone. Then today it rained again but I didn't drive through any especially major puddles yet once again that same problem came up. And as before flooring the pedal for a couple seconds made it go away. My guess is that water got into one of the sections of exhaust pipe, maybe through the flex section and into the catalytic converter. There are no holes in the pipe as far as I'm aware. And that flooring the pedal purges water back out. But that's just an uneducated guess. Anyone know what the deal may be?

 

Any codes? Is it possible you may have water leaking into the engine compartment? From above not below?

 

Well, I haven't checked the codes yet. But I've checked the air intake and the filter, with both being dry. Other than that I don't know how else it can enter the engine that would affect it in that way.

 

Power loss during rain/moisture usually points to the seal on the distributor cap

 

Exhaust section with O2 sensor taking a bath will cool it down and possibly make the ECU have a hissy-fit till its back up to normal temperature.

 

WHere is the O2 sensor located? and do I need a special tool to take it off and install it?

 

I've checked the distributor cap (for no reason at all at the time) but it seemed dry.

That is an excellent hypothesis. Definitely makes sense, but why hasn't it ever done that before? I suppose the fact that it hasn't been replaced in probably 7 years or so may have something to do with it..

 

I was having a similar problem, the alternator was getting wet and slipping. No battery light. I replaced the bottom plastic shield and quit having that problem in the rain.