i was washing my engine bay a few weeks ago & got water into the intake, and it ended up getting into the spark plug wires. the engine light came on & my car's exhaust was pulsating so slowly i thought i had a v8 all of the sudden. after i contacted a few honda experts, they suggested i unplug my spark plug wires & see how much water had gotten in, and then vacuum it out or get it out whatever way you can (i had to play small pieces of tissue paper in there to absorb the water since i couldn't find a portable vacuum. after i checked all the possible places for water, i connected everything back up, started up the car...and everything seemed fine again. the check engine light was still on, but they assured me that was normal & that i just need to reset my ECU again. so i did that, and everything's been fine ever since.

hope this helps.