What are spark plug wires and where are they located?

Your vehicle’s spark plug wires—also called spark plug cables, ignition wires, or ignition cables—play a very important role when it comes to starting your vehicle. Depending on the vehicle’s ignition system, spark plug wires transfer an electric pulse from your ignition distributor or individual coil packs that is received from the battery, to the spark plugs that are inserted into each engine cylinder in the order of the firing sequence. This, in turn, ignites the compressed fuel-air mixture in your engine’s combustion chamber, starting your car or truck.

In terms of connection, the spark plug wires start at the distributor, usually found near the valve cover at the top of the engine, and run to the spark plugs at the engine head. As technology progressed, the distributor in newer cars was eventually replaced by coil packs, and the wires start there in this case. Spark plug wires consist of a metal wire with connecting terminals at the end, coated in a jacket of rubber to insulate it. Either the rubber cover or the metal wire can wear down over time, leading to lost voltage and engine problems. 

How do I know if my ignition wires need to be replaced?

As your spark plug wires age, they build resistance and do not transfer the electric pulse as well as they used to. This is mostly due to contact corrosion, and deterioration of the insulated coating or jacket on the wires. If the insulated coating on the ignition wires is cracked or torn the electric pulse may arc to other parts of your engine—causing a misfire.

If the metal terminals become corroded there may be a loss of electrical power. This can result in abnormal flow of power to the spark plugs which leads to incomplete combustion of the fuel-air mix in the cylinder. Incomplete combustion can cause engine misfires or stuttering, rough idling, power loss or power surges, and loss of fuel mileage. It also causes more harmful gasses to be passed on to the exhaust system, which might make your vehicle fail an emissions inspection. Misfires or emission problems may cause your check engine light to come on. 

The rubber coating on the wires can be damaged by heat in the engine bay by chemicals which may have leaked into it. By simple wear and tear over time, or in some rare occasions, the wires may even be chewed by rodents. Cracks in the coating can cause electricity to arc from the cable to nearby metal components in the engine bay. This can result in many of the symptoms mentioned above. The arcing may also lead to radio interference or interference with other electronic systems in the car or truck. 

There are a number of ways you could inspect your spark plug wires. The first and most obvious way is to visually inspect the wires. Under well-lit conditions, check the rubber coating for cracks, wear, or loss of pliability. Check the terminals for corrosion. Look for scorch marks, which can be a sign of heat damage. You could also start the engine with the vehicle in a dark place and the hood open and see if there are any visible sparks. The electrical system is not necessarily under high demand during idling so arcing may not be readily apparent. You may use a spray bottle to spray a little bit of water onto the spark plug wires and see if that encourages any arcing. Finally, you could use a digital voltmeter to test the resistance of the ignition wires. Your owner’s manual should specify what the resistance should be.

If your spark plug wires are beyond repair and have failed completely, starting and driving your vehicle will definitely be a pain. Therefore, making sure that you have them replaced in a timely fashion is important.

Can I replace the spark plug wires myself?

You should replace your ignition wires as recommended by your car’s manufacturer. Most manufacturers recommend replacing your spark plug wires between 50,000 to 60,000 miles. It is also a good idea to replace your wires when you are replacing spark plugs, tuning up your car, or replacing other major ignition components such as the distributor or coil. Of course, you will also want to replace your ignition wires if they are not working. 

In many cases, replacing the ignition cables will prove fairly easy. Sometimes, though, you may have to remove other parts to access the cables. This does not necessarily make the task more complicated, just more time-consuming. In some cases, it may be easiest to reach the spark plug cables from underneath the engine. It is very important to route the spark plug cables to the correct ports. Your vehicle should have a guide for this somewhere under the hood. You could also carefully compare the new cables to the old ones and label each. An even better tactic would be to replace each wire one at a time to avoid confusion. Be sure to use any clips or shields that hold the wires away from the exhaust. This will prevent heat damage to the new wires. 

Need replacement spark plug wires?

If you are in need of replacement spark plug wires then you have come to the right place! At 1A Auto, we have a large selection of aftermarket spark plug wire sets for many makes and models, and at great prices. These cables will get your get vehicle back in working order again!

At 1A Auto, we make shopping for a replacement spark plug wires for your car, truck, SUV or van easy—we're here to help you select the right parts for your vehicle! Call our customer service toll free at 888-844-3393 if you have any questions about our aftermarket spark plug wire sets, warranty, compatibility or to purchase, or you can buy online.