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Spark Plug Wires (Signs Of Failure + 5 FAQs)

March 12, 2022

Spark plug wires are a crucial part of your car’s ignition system. Although spark plug wires don’t need as much maintenance as other car parts, changing them before they fail can save you a lot of time and money. 

But how do you know when it’s time to replace your spark plug wires
And what’s the best solution for replacing your spark plug wires

In this article, we’ll answer these questions and more, including how often you need to replace them and the potential issues if they’re not replaced

This Article Contains: 

Let’s get started.

What Do Spark Plug Wires Do?

When you turn your key, it completes a circuit that sends power from the battery to the ignition coil pack. The ignition coil creates a magnetic field to form in the ignition coil wire that transforms low voltage from the battery to a much higher voltage sent to the distributor. 

As the distributor rotor spins, the electrical current from the ignition coil moves from the rotor to the electrodes within the distributor cap in the correct sequence. 

It’s the job of the spark plug wires, or the ignition wire, to carry that high voltage electricity to the spark plugs

The high voltage in the spark plugs then creates a spark that ignites the air-fuel mixture in the engine’s combustion chamber. 

Spark plug wires are typically found in older vehicles using distributor based ignition systems. More modern vehicles use Coil On Plug (COP) ignition systems that don’t need spark plug wires. 

Most older cars use the carbon core wire as their original equipment. However, there are also spiral core wires for high performance applications.

Next, let’s look at some telltale signs of a bad spark plug wire.

Signs Of Failing Spark Plug Wires 

Spark plug wires play an integral role in your car’s ignition, delivering high voltage power to the spark plugs. Predictably, this type of high voltage load creates a lot of heat. With time, the ignition wiring can become brittle, crack, or break altogether. 

Faulty spark plug wires will affect your vehicle’s combustion. As such, the most common sign of a bad spark plug wire is decreased engine performance, acceleration, and fuel efficiency. 

Additionally, you may notice issues within the combustion chamber, leading to misfires and engine stalling. You may also see the illumination of your dashboard’s check engine light

Note that these symptoms can be very similar to those of a bad spark plug, so it might be worth installing a new spark plug or two at the same time. If these symptoms describe your current situation, inspect the spark plug cables. 

Upon inspection, if you see any of the following, your spark plug cables need immediate replacing: 

Next, let’s look at some frequently asked spark plug wire questions and answers. 

5 Spark Plug Wire FAQs

Here are a few common spark plug wire questions and their answers: 

1.  Should I Drive With A Bad Spark Plug Wire?

Being part of your vehicle’s ignition system, when your spark plug wires start acting up, it can make your car difficult or even impossible to drive. 

Additionally, driving with a faulty spark plug wire can cause excess unburned fuel to flow into the catalytic converter, potentially damaging that part as well.

If you suspect you have faulty spark plug wires, you should avoid driving and call a mechanic to install a replacement wire in your driveway. 

2. How Often Do I Need To Replace Spark Plug Wires? 

A quality ignition wire set can last you between 60,000 and 70,000 miles. However, it’s always worth replacing these parts before they fail and potentially damage other components.

3. What Happens If I Don’t Replace My Spark Plug Wires?

Spark plug wires aren’t actually made from wire — they’re made from delicate carbon fibers. However, carbon fiber isn’t very conductive, developing a low resistance. 

This low resistance serves the purpose of reducing interference, mainly radio frequency interference from the stereo. Other components like the charging system or windscreen wipers can also cause interference.

These fibers break down and separate with time, causing too much electrical resistance, which degrades the spark and leads to poor engine performance, combustion, misfires, and terrible gas mileage. 

If left unchecked, a damaged ignition wire can cause voltage leaks to nearby engine parts, arcing, severe performance problems, and even failure in other ignition components, requiring new ignition kits. 

4. How Much Does A Spark Plug Wire Replacement Cost?

The average cost of replacing your ignition wire set is $190 and $229. 

Parts can cost anywhere from $123 to $145. Note that spiral core wires will cost more than a carbon core wire replacement. There are many brands to choose from, depending on your budget: 

Labor costs will likely be between $67 and $85.

5. Can I Replace Spark Plug Wires Myself?

If you notice any damage to your spark plug wires, it’s best to have a replacement wire installed as soon as possible. 

Replacing the ignition cables yourself isn’t too complicated, provided you have some tools like a spark plug wire separator, the proper materials like silicone dielectric grease, some know-how, and about an hour to spare. 

It’s important to note that replacing a spark plug wire set is more complicated than basic vehicle maintenance. The mechanic must replace the wires one at a time, and the spark plug cables must precisely match the original equipment to ensure the proper firing order. 

If you’re new to this, your best bet might be to let a professional mechanic handle it. 

In this case, why not rely on RepairSmith

RepairSmith is an auto repair and maintenance solution boasting competitive, upfront pricing and a 12-month, 12,000-mile warranty. If that’s not enough, our ASE-qualified technicians will come to your driveway to install the new products. 

Final Thoughts

Although not requiring as much maintenance as other parts, spark plug wires form an integral part of your car’s ignition system. When these ignition cables inevitably wear out, they can experience voltage leaks and damage nearby parts. 

If you have some mechanical knowledge, you could replace them yourself. However, if you’re unsure, it’s best to let our professionals at RepairSmith handle the tune up.