Just to let any one know of a problem I have had.
I have a 2001 F150 Supercrew with 4.6
I have cleaned my engine many times on this truck at home and carwashes. The problem that developed on my last engine cleaning was the loss of 3 coil packs ($80.00 each aftermarket plus $15.00 each labor) I have 76000 mi so I had new plugs installed.
So be carefull if you feel the need to clean engine, mine will be dirty from now on.