Never do it while the engines hot. Warms alright but hot is bad. Although we have no distributors we do have coil packs. I try to avoid really drenching anything electrical. Like Tampa said light mists of water, just enough to remove the simple green. I would at all costs avoid using a pressure washer. Water tends to find it's way to things it shouldn't when pressurized. You can do it with a cold engine, but I've found slightly warm works best. It helps the Simple Green penetrate better. Oh, and as if I had to say it don't ever spray water into your throttle body or air cleaner....duh!