A cam phaser is a gear system in the engine of a car that adjusts the cam shaft position while the engine is running. Engine pressure passing through the cam shaft and cylinder head activates the cam phasers.
The gears in a cam phaser are controlled by the car's computer. All Ford vehicles that have been produced since 2005 have cam phaser systems in the cam shaft of the engine. Benefits of having cam phasers in a car are that they help increase fuel efficiency, decrease the power needed to turn the engine over and keep the camshafts in the optimal position.