Combustion is a complicated process. It involves various elements combined together and different parts working in harmony with each other to produce the power that will drive a vehicle. Combustion happens inside the engine cylinders, and at the heart of each cylinder is a piston. When you look at an animation of a four-stroke combustion process, you'll see the piston as the component that moves up and down inside the cylinder as different strokes happen. At the beginning of combustion, it's located at the top portion of the cylinder. It moves down as the intake valves open to allow the air-fuel mixture in. Upon reaching the bottom of the cylinder, it moves back up, compressing the mixture. When the piston reaches the top, the spark plug fires, causing an explosion that propels the piston down. When the part reaches the bottom, the exhaust valve opens and releases the exhaust gases. You will see the part attached to a rod that connects to the crankshaft. As the combustion takes place, the up and down movement of the part is transferred to the shaft, and this is the force that drives the wheels. The cycle happens many times per minute, and this is the process that enables your car to run great distances. Piston damage can cause engine failure. That said, replace it immediately when it fails. Find your needed replacement in our selection here at Car Stuff.