How often should spark plug wires be changed?

Spark plugs provide the electricity needed for combustion by igniting the atomized fuel in the engine's cylinders. However, for this they need a constant power supply. That's the job of your spark plug wires....

Spark plugs provide the electricity needed for combustion by igniting the atomized fuel in the engine's cylinders. However, for this they need a constant power supply. This is the job of your spark plug wires. And just like your plugs, wires wear out over time. Once they begin to wear out, the electrical charge supplied to the spark plugs can be unreliable, creating engine performance problems, including rough idle, stalling, and other problems.

There is no single rule that would govern all vehicles. First, your car may not have wires, like many newer models. These models use a coil on plug instead and the coils can last for a very long time. However, modern spark plug wires can also last much longer than they once did.

In most cases, your wires should last well beyond the 30,000 miles your copper spark plugs are rated for. However, there are other factors that can affect timing.

• Damage: The spark plug wires may be damaged. If the insulation is broken or there is an internal break, you need to replace the wires, even if it is not yet time.

• High Performance: High performance does not always mean long life, and some types of high performance spark plug wires may need to be replaced relatively frequently (every 30,000 to 40,000 miles).

• Increased resistanceA: Perhaps the best way to know if the spark plug wires need to be replaced is to check their resistance. You will need an ohmmeter for this and you will need to know the initial resistance of the wires. Check each wire and look for higher resistance levels than when originally installed, as well as higher resistance in individual wires (indicating wire failure).

With all that said, the best option is to follow the mechanic's advice to replace the spark plug wires. While modern cars don't need the regular maintenance that carbureted cars did, they do need regular maintenance and the plug wires eventually fail.