When I have to steam clean an engine , especialy for a customer, I always blow off the distributer inside and out and give it a very generous spraying again inside and out with wd40. I also spray the wires and plugs with it. I have never had one even think about sputtering the next day doing this but one time, just one, I was in too much of a hurry to do it and the next morning it wouldn't start. It was a forklift I worked on. I think it was 3 in the morning when they called me to come fix it so now I make sure I always use the wd40.
Normaly I hate the stuff and tell people to get rid of it , especialy if they have been using it on their guns since I am a part time gunsmith, but out of the 1001 uses they advertise the ignition systems on engines is actualy a good use for it.