The timing chain is an alternative to the timing (or cam) belt. Its job is to control the opening and closing of the engine’s valves by turning the camshaft and crankshaft at the right speeds. The timing chain is subject to wear and tear along with other parts in the chain drive mechanism, and should be replaced every 40,000 – 100,000 miles. As well as the expected wear and tear of moving mechanical parts, the timing chain’s demise will be further hastened by infrequent oil changes, impure oil or a depleted oil tank. When a timing chain becomes worn it will stretch, affecting the ignition and slowing down the opening and closing of the engine valves. This might result in a sluggish engine and difficulty starting, as well as producing some strange noises such as rattling or squealing. You could more than double the timing chain’s lifespan if you look after your engine and change the oil regularly. However, do be sure to replace it (and its accompanying parts) when worn, or it could break and cause severe damage to the engine.