Sorry to dig up an old thread... First post here BTW...
But I washed my ls400 1992 engine at the local DIY carwash. I used their low-pressure engine degreaser and the low-pressure spot free rinse... It's SPOTLESS! But... now it won't start. :) I'll let you all know how much it cost to fix and what I broke.
Crappy thing is... I do this all the time and have NEVER had a problem! I would say I've washed the engine compartment around 30 > 40 times.