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

[Patrick L.]

Its been done for years. Its best to use a spray bottle and not pour it in. Raise the idle speed and start spraying which will steam clean the cylinders, don't let the engine quit. It came back into vogue during the early days of computer controls as these engines would build carbon to the point of knocking. GM even sold pressurized cans of water just for this purpose.