Top Engine Cleaner removes carbon and other deposits without harming engine parts, oxygen sensors or catalytic converters. Blend of solvents, surfactants, emulsifiers, penetrants, lubricants and FX216, a special patented ingredient. Cleans intake valves, upper cylinders, compression rings and carburetors. Eliminates sticking intake valves, sticking piston rings and carbon knock that result in drivability problems including hard starting, stalling and poor emissions.