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Your Guide to Spark Plug Wire Replacement

Spark plug wire replacement

Spark plug wire replacement can help you save some cash as driving on faulty spark plugs or spark plug wires may result in increased fuel consumption. High-quality wires will not only allow your spark plugs to start faster but your engine will also run more efficiently. So it is a good car ownership habit to change your spark plug wires regularly.

Auto Repairs Are EXPENSIVE


Spark plug wire replacement should be included on your car maintenance checklist to make sure your vehicle is working at its optimal level. The spark plug wire needs just as much attention as the spark plug itself considering that it is the wires that are responsible for charging the spark igniting each spark plug.


Spark plug wires also wear out because they are not actually made of wire but of delicate carbon fibers that break down over time as the fibers separate, with the end result of electrical resistance. That high resistance will degrade the spark plug, and that results in engine misfires, poor combustion and plummeting gas mileage. You will eventually see the “Check Engine” light illuminating.


If you leave out spark plug replacement long enough then the wires will eventually start leaking voltage to its nearby engine parts, causing serious engine problems, arcing and even causing the ignition component to fail.


Spark Plug Wire Replacement: The Basics


A smooth running engine has good spark plug wires. When you have an aged or faulty spark plug wire the high current of electricity that flows through it can bypass the protective rubber coating and in the absence of insulation cause the current to connect with any metal object near it. When this arcing happens it reduces the flow of current to the spark plug and that also means reduction or even loss of the spark from that plug. And when that happens it reduces the power of the combustion on that plug affecting the idle and the performance of your vehicle as a whole. That’s also the cause of higher fuel consumption.


If the arcing has managed to eliminate the spark altogether, it will result in a noticeable “lope” as the engine idles since the plug is not firing. And when this happens it can damage the catalytic converter as it passes unburned fuel through the exhaust. This will cause you a huge bill as a new catalytic converter could run up to $350 plus excluding the installation.

Does changing spark plug wires make a difference?


If you should ask if spark plug wire replacement makes any difference, then the answer is a big YES. As mentioned earlier it will make a huge difference on how your engine performs. A good spark plug wire will provide an instant spark to your vehicle's spark plug as opposed to that of a Standard OEM wire. That subpar spark plug wire may be able to start the car fine at first, but they will eventually deteriorate and lose their ability to properly start your engine. This may result in a lower idle, loss of power and even an engine misfire. Strong and durable cables are responsible for holding the spark until it reaches the spark plug, boosting your vehicle's performance.


Changing your spark plug wires regularly could also improve your car’s gas mileage. Running on faulty spark plugs or spark plug wires, on the other hand, may result in increased fuel consumption. Wires that are high in quality allow the spark plugs to start faster causing your engine to run more efficiently. With this, having spark plug wire replacement part of your routine maintenance checklist, as mentioned, will help you cut your gas expenses. It will also help you save up on repairs or from not having to change your spark plugs as a whole.


Running on defective wires can cause damage to your vehicle if the wires are not replaced quickly enough. You may end up damaging the actual spark plugs, resulting in a much larger repair bill. Spark plug wire replacement also has an effect on reducing radio frequency interference or RFI. Spark plug wires are made of carbon, which makes them more resistant to other electronic frequencies. This contributes to a reduction in the amount of radio frequency interference generated by normal ignition system operation. RFI can disrupt radio reception and interfere with the car's sensors and computer systems.

What are the signs of a bad spark plug wire?


Since the spark plug wire is an essential part of a vehicle’s electrical system as it transports electrical power from a vehicle's ignition system to its engine spark plugs it must function properly to secure normal engine operation. When spark plug wires fail, it can lead to a variety of engine problems and here are the signs to watch out for:


Visible Damage


Before anything else you must check the spark plug wires for visible damage first. Examine the surface for any signs of melting or cracking. The following situations will require immediate spark plug wire replacement:


  1. Damage due to vibration – Engine vibration causes constant wear and tear, which can loosen the electrical connection at the spark plug. This raises the voltage required to fire the spark plug, potentially damaging the ignition coil as well as the spark plug wires.


  1. Damage due to heat – Engine heat can cause wire insulation and boots to burn. A faulty boot can obstruct proper spark plug wire seating and performance. Damaged wire insulation can allow voltage to jump to ground rather than the gap at the bottom of the spark plug.


  1. Damage due to abrasion – When spark plug wires rub against engine parts, particularly sharp edges, the insulation is cut and broken. When this occurs, voltage can jump to ground rather than reaching the spark plug.


Engine Performance Signs


  • Engine is hard to start


Once spark plugs wires become too damaged it will fail to do its job to send enough current to spark ignition so the engine will fail to start.


  • Engine Misfire


Another common symptom of bad spark plug wires is an engine misfire, which occurs as a result of erratic or incomplete engine combustion. Bad spark plug wires frequently cause erratic electrical current flow to the engine spark plugs, alternating between brief periods of normal flow and brief periods of abnormal, erratic flow. As a result, there are periods of erratic and incomplete engine combustion, which can result in an engine miss.


  • Rough Engine Idling


A rough engine idle is the most common symptom of faulty spark plug wires. Spark plug wires are in charge of transmitting electrical current from a vehicle's electrical system to the engine spark plugs, where it is used to ignite the engine's air/fuel mixture. Spark plug wires that are damaged can obstruct the normal flow of electrical current to a car's spark plugs and that will result in a rough and erratic engine idle.



  • Engine Hesitation


Engine hesitation, which is most noticeable during acceleration, is a condition caused by either abnormal fuel flow to an engine or abnormal electrical conduction to a vehicle's spark plugs. Spark plug wires that are damaged cause an engine to hesitate if they disrupt the normal flow of the electrical current traveling from a car's battery to the engine spark plugs. They either have degraded internally or developed some cracks in their outer coverings, that damage causes electrical interference.


  • Engine power has been reduced.


To ensure proper engine combustion and engine power, proper electrical conduction to a vehicle's spark plugs is required. Any flaws in a vehicle's electrical system, including its spark plugs and spark plug wires, can have a negative impact on spark plug firing, affecting engine combustion and engine power. Bad spark plug wires can significantly reduce engine power by inhibiting or interfering with the normal flow of electricity to a vehicle's spark plugs.


  • Surging Engine


An engine surge is a common symptom of a vehicle electrical problem. It occurs when a vehicle experiences brief bursts of adequate electrical flow to its spark plugs, interspersed with brief periods of reduced or nonexistent electrical flow. Engine surging is a common symptom of bad spark plug wires, particularly if the wires have cracks or breaks in their outside insulation, which can create significant electrical resistance and lead to abnormal or completely stopped electrical flow to a vehicle's spark plugs.


Other Symptoms Pointing to Bad Spark Plug Wires


  • If you smell what seems to be a raw gas odor coming from the tailpipe then it could be due to an excessive amount of fuel that is going through your vehicle’s engine as the faulty spark plug wires are causing the engine to burn more fuel than it needs to combust.


  • A ticking noise that changes pitch with RPM can also possibly point towards faulty spark plug wire.



What Causes Spark Plug Wires to go Bad?


There can be many possible causes of spark plugs going bad but the most common reason spark plug wires can go bad prematurely is because of its surrounding condition or environment. For example, when an engine generates and radiates too much heat it can result in the spark plug wires insulation melting and causing damage to the wires. In the absence of the insulation, the possibility of sparking in there causing damage becomes even greater.


Another possible issue is that the engine is responsible. The vibration coming from the engine can stretch the spark plug wires resulting in a loose electrical connection. Another common reason for the spark plug wires going bad is a bad car battery. To prevent this from happening be sure to use not only a good car battery but also good spark plug wire holders as well.


And you will also need to consider the possibility that the spark plug itself can cause the trouble. lf the spark plug has issues it will have the tendency to draw more current to the engine and when this happens it will also affect the spark plug’s wires' life. Take note to always check the gap of the spark plug. If you notice that there is more or less gap than what is normal, then it will also cause the spark plug wires to go bad faster.



How much does it cost to replace spark plug wires?


The labor costs for spark plug wire replacement are estimated to be between $65 and $82. The parts you will need may cost $121 to $143. Taxes and fees are excluded in these estimates, and do not factor in your unique location or your specific vehicle. Related repairs you may need are also not included. So you will also have to consider these other possible expenses.

Why is spark plug replacement so expensive?


So why is spark plug replacement costly? Back in the old days a tuneup needed to be done annually to maintain the car. This job requires the mechanic to replace the spark plugs as well as the points and condenser. They also need to check or replace the rest of the ignition system. But now, replacement of spark plugs is no longer an annual thing so most car manufacturers stopped making the spark plugs accessible. So in the event that you need to replace them it will also entail removing other parts like the intake manifold and it takes a lot of work, effort and time to reach the spark plugs meaning more cost on labor.



It always pays to do the spark plug wire replacement before they even wear out. It is recommended that they also be changed when you change your spark plugs usually between 60,000 to 100,000 miles or depending on what your owner user’s manual suggests. There are already a lot of materials and tools available to help you do a quality job of your own.


If you are up to it you can even save an hour of shop labor charges worth. First step is to know the basics of knowing if you have a faulty spark plug wire so you will no longer need to pay that costly diagnostic fee just to have your worn spark plug wires investigated. The whole task is pretty easy and hopefully this article has been helpful.


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