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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.
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 idl - 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.
- 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 Mufflers
There are three types of mufflers and which is best for your car depends on your desired balance between noise and air flow. High-performance mufflers, which add horsepower to the engine, have a lot of air flow but also make the most noise. The stock muffler on your dad's sedan may not offer much in performance but probably purrs like a kitten.
- Glass Pack Mufflers - This is a straight-through design (it looks like a plain tube) and the simplest type of muffler available. A glass pack offers a good balance between noise and performance and isn't likely to wake your neighbors when you drive home at night.
- Chambered Mufflers - This is a common design on most cars and uses several dampening chambers inside the muffler to reduce noise as exhaust travels from chamber to chamber. These mufflers have the rectangular shape you're used to seeing when picturing the typical muffler.
- Turbo Mufflers - This is what you want for performance and, despite the name, doesn't require even a turbocharger under the hood. Turbo mufflers use an s-shape inside the chamber to dampen some noise while maximizing performance.
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 Pick the Right Spark Plug Wires for Your Vehicle
Not all cars use spark plug wires, and spark plug wire kits are designed to fit specific vehicle makes, models and years, so check your vehicle information to see what your manufacturer recommends. In general, you should replace your wires with the same type originally used for your car. For instance, cars with distributed resistance wires should use the same type of wires for replacements.
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."
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 most vehicles, this will be about every 20,000 to 40,000 miles. However, wires may often last longer. You can use an ohmmeter to check your wires' resistance and compare it with their original resistance in order to evaluate how worn your wires are. For best results, check your owner’s manual for your manufacturer’s recommendations on spark plug and wire replacement.
How much does it cost to replace spark plug wires?
The average cost to replace a set of spark plug wires is between $157 and $238. This includes $96 to $160 for parts and $61 to $78 for labor.
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.