Go to autozone and buy a can of CD2 engine detailer. Cover up any electonics, wires, etc. Spray most the can freely on the engine bay. Avoid spraying directly in the intake or any such vital areas. Let it sit for 20 minutes, and wipe of the excess. The stuff is amazing. Not spraying your car down with a hose or pressure cleaner, and no harsh chemicals that f@#k anything up. It works on the metal and plastic parts of the bay. I did this a few months ago and it works awesome.