Click and Clack at it again - De-carbonizing an engine.

[J Franklin]

In auto shop we were told to add water as a mist while the car ran and increase mist till is stalled out (don't pour it in). let it sit overnight and don't restert it near the garage door or you will need to clean the door of carbon soot.

Your car will run nice in a rainstorm because the water vapor in the air expands entering the hot cylinder and gives a compression boost.