Does the 2004 Mazda 3 have a timing belt or chain?

For the 2004 Mazda3 both the 2.0 L 4Cylinder and the 2.3 L 4Cylinder engines use a timing chain rather than a timing belt. Since it uses a timing chain it doesn't need to be replaced unless it's stretched or if it completely fails. If it used a timing belt it would need to be replaced every 60,000 to 100,000 miles or so. The reason why timing chains usually don't need to be replaced is because they are in the engine and aren't as exposed as the belt which is outside the engine. If the chain ever does fail the cost of a new one is anywhere from $80 to $140. It is a lot better to use a chain because it saves You the headache of having to get it replaced as often as the belt.