Originally Posted by 04 Quadcab

Don't know how you'd do it with fuel injection, but back in the day of the carburetor we used to clean the entire combustion chamber with water (yes, water). We'd pour water slowly down the carb, just balancing it so that the engine struggled but didn't die. Cleaned everything real well; guess you'd call it steam cleaning. Had to be careful not to get too wild and pour it in fast enough to hydrolock the engine (water isn't compressible). Obviously, not a good thing.
There are petroleum products such as Seafoam that can be used as I describe, and I think they'll kill the combustion process before reaching the hydrolock point.