Guys, I hope I don't jinx myself but I am starting to think the rough idle & check engine light was the result of washing my engine. It hasn't done it in a while now and I'm guessing that water got into a a bad spot but it's dried up now. I haven't done anything to the car since (no spark plug or wire changes)and I'll just keep an eye on things.

So in the future if I want to clean the engine, what's the safest way to do it?