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6 Common Sign & Symptoms Of Bad Spark Plug Wires Explained

Symptoms Of Bad Spark Plug Wires

Like bad spark plug symptoms, do not overlook bad spark plug wires symptoms. The symptoms of bad spark plug wires are pretty similar to that of bad spark plugs, so it can be easy to determine for some of you who are well aware of the effects.

Symptoms Of Bad Spark Plug Wires

If you have no idea about any of the symptoms, then read our article to know them in detail.

6 Symptoms of bad plug wires include-

  1. Car engine hesitation
  2. Noises inside the car
  3. Decreasing engine power
  4. Engine surging
  5. Slow acceleration
  6. Decreased gas mileage

What are the Symptoms of bad plug wires? [discussed]

Symptoms Of Bad Plug Wires

1. Car engine hesitation:

When the wires fail to supply inadequate current flow to the engine from the spark plugs, engine hesitation occurs.

As that point outs, your spark plug wires need changing as they have worn out for a reason.

Due to engine hesitation, your vehicle might face impromptu breaks while traveling.

2. Noises inside the car:

Another symptom of a bad spark plug wire is knocking noises from the vehicle.

The noises occur when the combustion chambers are not working correctly, and the pistons have to work forcefully. The noises can increase day by day if you do not change the bad spark plug wires.

3. Decreasing engine power:

For the engine to run smoothly and steadily, the spark plug wires must be in good condition to create combustion and power itself.

Therefore, when the spark plug becomes faulty, the engine will not have the optimum strength to work and show dying symptoms.

Thus, changing the spark plugs as soon as possible can save your engine!

4. Engine surging:

Broken or damaged spark plug wires can lead o engine surging. When you notice this, take immediate action to change the bad wires that can save your engine.

The surge mainly happens when the worn-out wires fail to take sufficient electrical flow to the engine. Hence, the engine does not pick.

5. Slow acceleration:

It is a very common and easy symptom to tell if the spark plug wire has gone bad.

Bad spark plug wires will undoubtedly not create enough electrical power for the combustion chambers to accelerate the car.

Hence, the acceleration rate seems to decrease or slow down more than usual. To ensure a smooth and fast acceleration, change the bad spark plugs and their wires too.

6. Decreased gas mileage:

Another easy symptom to determine bad spark plug wires, yet the most irritating one is falling gas mileage.

Your journey gets shortened as the vehicle’s gas starts to cover less mileage than before due to faulty spark plug wires.

Therefore, you have to spend more money on the petrol pump. Changing the defective spark plug wires is less expensive than 2-3 times gas/ fuel injection in the car.

2 Top Reasons why spark plug wires go bad:

Top Reasons Why Spark Plug Wires Go Bad

1. Poor handling:

Poor handling is an unintentional reason that causes the spark plug wires to break or slit. When servicing the car, one can accidentally harm the wires, and it remains almost unnoticeable.

So, if you handle the parts and even the wires with care, such accidents won’t happen.

These are quite sensitive things because even if it harms no one, your entire car will face troubleshooting.

2. Age:

As the car ages, the spark plugs and their wires also wear out. Obsolescence is bound to happen, so you have to keep replacing the spark plugs after a certain period, as mentioned in your vehicle maintenance booklet.

What does an engine misfire sound like

The sound of an engine misfiring can involve a loud popping noise. This sound comes from a misaligned spark plug or another engine-related issue. The popping sound is often accompanied by vibration and is usually followed by a rough idle. If the misfire is severe, the engine may stall, and all the lights on the dash may light up. 

How to replace spark plug wires

1. Tools you need

Before you start, ensure you have all the necessary supplies and tools, including the correct type and size of spark plug wires, wire cutters, ratchets, socket wrenches, and pliers. 

2. Locating spark plug wires

The first step is to locate the spark plug wires and mark them in their installation order. You can locate the wires on the distributor cap and mark the corresponding numbered spark plug wires matching the position of your vehicle’s engine.

3. Removal

Once you’ve located the spark plug wires, the next step is to remove them. Remove the distributor cap first, then using a ratchet or socket, remove the spark plug wire from the distributor.

4. Installation

When installing the new spark plug wire, make sure the end with the largest diameter is pointing towards the spark plug. 

5. Testing

After you’ve replaced all the spark plug wires, test the ignition system by starting the engine. If it starts, you’ve successfully replaced the spark plug wires. 

How do you know which cylinder is misfiring?

Here’s how to do it:

1. Listen To The Engine

One of the most effective ways to identify the misfiring cylinder is to listen to the engine. The misfiring cylinder will sound duller than the other cylinders.

2. Check Your Car’s Computer

Your car’s onboard computer will record any engine performance irregularities and display them on the dashboard or console. 

3. Check The Spark Plugs

Spark plugs are integral to a car’s ignition system and are responsible for delivering electricity to the cylinders. They can become worn or damaged over time, leading to misfires in certain cylinders. 

4. Fundamentals Of Car Diagnosis

Finally, you can use the fundamentals of car diagnosis to identify which cylinder is misfiring. Pull each spark plugs and inspect them to see if they’re all igniting properly. 

The necessity of Replacement of bad plug wires:

No one would like to travel with an inefficient and slow engine, as they lead to so much frustration.

You will also have to keep re-visiting the gas station more often and spend money as faulty spark plug wires are eating up the gas fast.

Therefore, good-conditioned and high-quality spark plug wires will satisfy your journey in every possible way, with your engine running faster and smoother than ever.

That is why the bad plug wires need replacement.



Can an individual spark plug wire be changed?

Yes, you can change individual plug wires if you feel it has got damaged. But if you have the budget, then changing all at once will save you from the hassle.

Will changing spark plug wires improve the performance of the vehicle?

Of course, the spark plug wires work as a medium to provide power to the engine from the spark plugs. If the medium is working fine, then the performance is bound to improve.

Will I see all the symptoms at once?

Not necessarily; you will see all the symptoms. Initially, you will see one or two signs. If overlooked, then other symptoms might follow as well.


The plug wires are as important as the plug themselves as they run the engine. If you keep ignoring the symptoms, then engine failure will more likely happen.

Therefore, if you see any of those symptoms, you must get the wires changed. Changing the wires won’t cost you much, whereas changing the entire engine will cost significantly.

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