only if u get over a tablespoon in the cylinders but as ur running the car its constantly burning it out as well as breaking up any carbon build up built on the side walls and it burns it thru the engine, if ur just spraying water into it u can hear it slow down, just spray it slowly, this is the same as any other carbon buildup cleaner so dont be afraid to try it, if u want take a look at an intake manifold cleaner at ur local autozone and read the instructions on there, almost all of them are used the same way. its not easy to hydrolock the car unless ur "dumping" water into the intake, small amounts will just blow right thru. but ur looking for a fine mist thru a squirt bottle like 2 sprays every 10 seconds and u'll hear the engine slow down and rev back up while ur doing it.