I routinely pressure wash all my vehicles engine bays. Every vehicle I have EVER owned, I pressure wash the engine bay, and occasionally will roll around on the wet ground to pressure wash the undercarriage and transmission/oil pan/backside of the brakes, differential, etc.
NEVER have had a problem. Been doing this since 96 when I got my first new truck, a 96 F-150.
I usually use some simple green to spray down the engine bay, let it set about ten minutes, then just pressure wash it off. When done and dry, use some CD-2 Engine Detailer spray and coat the entire engine bay, fender to fender, firewall to radiator. This stuff kicks ass, it shines up the engine bay, and seals everything off from being stained with dirt and road film. After a while, dirt will start to stick to it, but the detailer makes it super easy to power wash it all back off again with a little simple green, and you just re-spray the engine bay down and you're done. Looks like a show car under there, and alot nicer to work around because you are not dirty up to your elbows if you do any work under there.
All electrical connections on newer cars are water tight, and usually have a two, three, or more rubber lip sealing the connector from the elements. And since these things dont use a distributor, that's the only thing you'd ever have a chance of having problems with due to moisture, yet my Rams, my 96 Integra GSR, and my old F-150 that I long since traded off, all had distributor ignitions, and I routinely pressure washed the engine bay, and never, ever had a problem.
