The automobile engine provides the locomotive force for the vehicle. Essentially, an engine is a device which converts fossil fuels (gasoline) into kinectic energy. Gasoline is injected into a cylinder, compressed and ingited – this causes an explosion. Thousands of these little explosions drive the pistons rapidly and this motion is transfered to the crankshaft which ultimately gets transfered to the wheels via the transmission. Gasoline and diesel powered engines used in automobiles and light trucks may vary in size and design, but they all share the same operating principle. All of these engines are known as four-stroke internal combustion engines.

Four-stroke describes the operating cycle of the engine. Each cylinder of the engine will fire once every two rotations of the crankshaft. The first stage of the cycle is called the intake stroke. As the piston moves down in the cylinder the intake valve opens, drawing the air/fuel mixture into the cylinder. As the piston reaches the bottom of the cylinder, the intake valve closes and the rotation of the crankshaft moves the piston upward in the cylinder. Both the intake and exhaust valves are closed during this cycle and as the piston moves upwards the air/ fuel mixture is compressed. This is called the compression stroke.

The compressed air/fuel mixture is ignited as the piston nears the top of cylinder. The expanding gases that result from the ignition of the air/fuel mixture, forces the piston down in the cylinder. This is called the power or ignition stroke. This is the cycle that produces the force that moves the crankshaft and allows the engine to rotate. The piston moves down to the bottom of the cylinder and the rotation of the crankshaft moves the piston back upwards in the cylinder. As the piston moves upwards, the exhaust valve opens and the burned air/fuel mixture is pushed out of the combustion chamber. This is called the exhaust stroke. This is a simplified explanation of the basic operation of an engine. There are many components involved in keeping an engine operating