Spark Plug Wires

FAQs Concerning Spark Plug Wires

What do spark plug wires do?
Spark plug wires, also known as spark plug cables, ignition cables, high tension leads or high tension cables perform a couple important functions. Their primary purpose is to deliver electrical current to each of the spark plugs from a distributor, ignition coil or magneto. In the process of doing this, they must also suppress electromagnetic interference, which can disrupt on-board computers, wireless signals, radios and speakers.
How long do spark plug wires last?
A quality set of spark plug cables will typically last 60,000 to 70,000 miles. Longevity may vary with brand and use. We recommend replacing your spark plug wires whenever you replace your spark plugs.
What causes spark plug cables to wear out?
Spark plug wires are covered by an insulating heat-resistant material such as silicone or synthetic EPDM rubber, which gradually wears down over time due to the heat passing through the wires. Cables can also be damaged by tugging on them, oil leaks, moisture or terminal corrosion.

Signs Your Spark Plug Wires May Need Replacement

When your spark plug wires are starting to wear down, you will usually notice some telltale signs:

• Check engine light - This could indicate a problem related to your spark plug wires as well as other possible issues.
• Erratic idle - Problems with the current flow to your spark plugs can cause rough idling, which is one of the most common symptoms of deteriorating spark plug cables.
  n- Engine misfire - Disruptions to current flow caused by deteriorating spark plug wires can also cause engines to miss, hesitate during acceleration, alternate between surges and stops or generate reduced power output.
• Failed emissions test - Engine misfire due to spark plug wire problems can lead to elevated hydrocarbon emissions or generate a fault code signaling cylinder misfire.
• Reduced fuel mileage - Faulty spark plug firing can lead to reduced efficiency, lowering your fuel mileage.
• Radio interference - This can indicate electromagnetic interference caused by deteriorating spark plug wire insulation.
• Visual damage - Visual inspection of your wires can reveal cracks, abrasions or burns. Observing your engine run in the dark can also allow you to check if sparks are escaping from the wires.
• Electrical ticking sounds when engine running - If you run your engine and listen for a ticking sound like a static electricity discharge, this can indicate a spark plug wire problem.
• Irregular resistance in one wire - If you check your wires' resistance with an ohmmeter and find that one wire has notably different resistance than the others, this can indicate a faulty wire.

Types of Spark Plug Wires

There are three main types of spark plug wires:

• Distributed resistance wires - Also known as carbon core wires, distributed resistance wires were used on 95 percent of cars manufactured prior to 1980. They are made of fiberglass-impregnated carbon, which creates high resistance to electromagnetic interference in car radios and electronics.
• Magnetic resistance wires - Mag wires use a wound spiral core made from a copper nickel alloy. This provides less resistance, allowing spark plugs to fire with less current while relying on the coiling to reduce electromagnetic interference.
• Fixed resistor wires - This type of wire is found mainly on European vehicles. It employs a copper or steel wire, with a resistor inserted inside the plug boot to suppress electromagnetic interference.

How to Install Spark Plug Wires

Replacing spark plug wires involves disconnecting your battery for safety, disconnecting both ends of each old wire and replacing each wire with a new one. To make sure you replace them correctly, take note of how each wire is installed before disconnecting them, or even take a photograph and remove only one wire at a time. Using a special tool called a spark plug boot removal tool will make it easier to replace your wires without damaging your spark plugs. On older vehicles, you may also need to replace your distributor cap. For more detailed instructions, see the article on How to Replace Spark Plug Wires.

Additional FAQs

How often should I replace my spark plug wires?
To keep your car running in the best shape, you should replace your spark plug wires whenever you replace your spark plugs. For some vehicles, this will be about every 20,000 to 40,000 miles. Consult your owner's manual for the replacement interval on your vehicle.
Can I replace my spark plug wires myself?
Yes, learning to replace spark plug wires is fairly easy. It should take you about an hour once you learn how to do it.
Is there a way to make my spark plug cables last longer or run better?
One way to extend and improve the performance of your spark plug wires is to periodically clean them. You can do this with a rag, WD-40 and dielectric grease. This will also give you an opportunity to inspect your wires for wear and tear.
Buy spark plug wires online or visit your local Advance Auto Parts store and have one of our knowledgeable Team Members help you.