Driven by the crankshaft, the timing belt keeps internal engine components in sync by causing valves to open and close at the proper time.

In order to maintain the mechanical integrity the engine needs to operate, engine components must be in precise synchronization. If the timing belt is loose or improperly adjusted, it may "jump time" (skipping a tooth or more, usually on the cam gear). This results in a loss of synchronization and engine performance.

In addition, because the timing belt is made from rubber and reinforced with fiber cords, it naturally degrades over time. It should be replaced at scheduled intervals, which vary among car manufacturers, but are usually every 60,000 to 90,000 miles.