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Q: When Should Spark Plug Wires Be Replaced?

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When should spark plug wires be replaced?

When deciding to replace your spark plug wires, you should first check your owner’s manual. Follow the recommended maintenance schedule that the vehicle manufacturer has published.

Besides regular maintenance, another reason to change your plug wires is due to failure, which can happen at any time.

Some causes of spark plug wire failure include:

  • Coming into contact with motor oil which deteriorates the plug boot and wire insulation.

  • Spark plug wires chafing against a bracket which allows the spark to jump straight to the engine block and bypass the combustion chamber inside the engine altogether.

  • Poor contact due to corrosion inside of the plug wire connections.

Symptoms of plug wire failure can include poor idle quality, lack of power, engine misfire, emissions test failure, or decreased fuel economy.

An old mechanic rule of thumb was to replace the plug wires with every major tune-up, which included spark plugs, distributor cap and rotor, and points and condenser. Nowadays, that rule of thumb is largely ignored because of more advanced systems, better materials, and higher quality production values.

If any of these issues are familiar to you and you think your vehicle may need to be checked out, have a qualified mechanic inspect and replace your faulty spark plugs as necessary. A healthy car is a happy car.

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