Not all spark plug wires are created equal. And because moving electricity to the plug to produce a spark is so critically important, using the wrong wires for your vehicle, damaged wires, or poor-quality wires will undoubtedly lead to problems down the road.
As electricity travels along the plug wires toward the plug so it can generate a spark, it’s also looking to do something else – escape. The electricity is looking for any opportunity to jump from the wire and instead head down the path of least resistance. When it finds the escape route it’s been searching for – usually in the form of missing or damaged wire insulation – the results can include engine misfire, poor fuel mileage, hard starts, rough idles and lack of power. Electricity also generates radios waves and if it escapes from the plug wires can interfere with a vehicle’s radio and other electronics.
The plug wires’ insulation is what keeps the electricity from escaping, and high-quality wires will have more insulation that’s made from durable components that are better able to resist wear from vibration and heat. Over time, the engine’s heat cycling takes its toll on even the best spark plug wires, which is why replacement is recommended by many manufacturers at 100,000 miles.
There are primarily three types of spark plug wires:
- Distributed resistance wires are constructed of fiberglass-impregnated carbon. Also known as carbon core wires, they were the standard on about 95 percent of vehicles before 1980.
- A shift to inductance or mag (magnetic resistance) wires accompanied the rising popularity of Asian vehicles. Featuring a spiral wound core of a copper nickel alloy, the material presents less resistance to the electricity flow, meaning less current is needed to generate the spark, and at the same time the winding pattern and materials help prevent any Radio Frequency Interference (RFI) from escaping.
- Lastly, there are fixed resistor wires. These are often found on European vehicles and feature steel or copper wire and a resistor inside the plug boot to control interference.
Troubleshooting spark plug wires
If you think your vehicle might be having some issues caused by faulty plug wires, begin the diagnosis with a close inspection of the wires’ condition. Examine them for heat-induced cracks or abrasions caused by rubbing against other parts. Look for areas where they’ve been burned through because of contact with an exhaust manifold. Also try examining the engine in the dark, looking for visible sparks where the electricity is escaping along the wires, and also listen for an electrical ticking sound, similar to what you hear when you receive a big static electricity shock. Also measure the wire’s resistance with an ohmmeter. One plug wire with a resistance that’s significantly different than the other wires could indicate that’s the problem wire.
When installing new wires, make sure you’re using wires specified for your vehicle. Characteristics such as the wire length or a boot that attaches using clips as compared to a thread-on boot matter when it comes to performance. Also avoid problems by routing new wires in the same manner that the previous wires were, and removing and replacing the wires one at a time.
Using the best spark plug in the world won’t make any difference to your engine if that plug can’t get the electricity it needs, so choose and install plug wires wisely.