4 Common Signs of Bad Spark Plugs and Wires

Spark plugs and wires play an essential role in your car’s electrical and ignition systems. Spark plug wires transfer electrical power from the distributor or ignition coil to the spark plugs.

In turn, spark plugs carry the charge to the cylinders to propel the combustion process in the engine.

Faulty wires can affect the car’s performance and lead to costly engine problems, but sadly, many people ignore the troubling symptoms. When spark plugs start to go bad, they tend to show signs such as visible damage to the wires and cause the car to idle roughly, misfire, or hesitate. Learning the symptoms of bad spark plug wires is crucial, so you have the tools you need to address the problems early on and avoid costly damage to your vehicle. 

If your car needs new spark plugs and is showing other warning signs, you may be able to hold the manufacturer liable under your state’s lemon laws. These laws protect consumers when they purchase a vehicle (a “lemon”) that needs excessive repairs or is dangerous to drive because of a defect. 

Robison Lemon Law Group exclusively advocates for consumers who unknowingly buy vehicles with defects that cause the cars to be unsafe to drive, have a substantially impaired value, or require repeated repairs. We believe that consumers should not have to pay for and drive unsafe vehicles, and we understand that many consumers who find themselves in these situations feel trapped. 

We help consumers like you fight for your rights under state and federal lemon laws to pursue the compensation they deserve under the law. Our lemon law lawyers have helped numerous clients obtain a replacement vehicle, a refund from the manufacturer, and due compensation at absolutely no cost to them. 

What Is the Difference Between Spark Plug Wires and Spark Plugs?

Spark plugs and spark plug wires perform vital roles in helping your engine run smoothly. But what are they, and what is the difference between these two components?

Spark plugs play a crucial part in the life of a combustion engine: they are responsible for the spark that ignites the air and fuel in the cylinders to power the engine. The spark plugs are highly durable (after all, they are made to instigate and withstand small explosions within the engine), but they can become faulty, erode, or be defective. 

In contrast, spark plug wires (also called ignition cables or wiring) connect the coil that houses the initial spark to the spark plugs. When you turn on the ignition, it creates a charge that travels through the spark plug wires into the spark plugs. From there, the charge goes into the cylinder or crankshaft to initiate the combustion that powers the engine. 

While both play similar roles in the combustion process by acting as conduits, spark plugs and spark plug wires are two distinct car components. When these parts deteriorate or are defective, they tend to show similar signs. Reasonable minds differ, but many professionals recommend simultaneously replacing the spark plugs and the spark plug wires. 

What Are Common Signs of Bad Spark Plugs?

If your car starts showing the following signs, it may be time to replace your spark plugs or spark plug wires:

  • There is visible damage on the spark plugs or wires, 
  • The engine is idling rough, 
  • The engine hesitates, or
  • The engine misfires. 

In some cases, you may be able to recoup your losses for repairing or replacing the spark plugs or wires under your state’s lemon laws. If a defect, such as a burnt valve seal, is causing or contributing to the spark plug issues, you may be able to obtain a replacement vehicle or a refund. 

1. Visible Damage on the Spark Plugs or Wires

Visible cracking or melting is one of the signs of bad spark plug wires. Spark plug wires may start to dry out over time, so look for cracks in the insulation. The wires can also start to melt if they come into contact with certain hot components of the engine. Make sure you inspect the entire length of each wire to ensure you do not miss any visible signs of wear or tear. The wires are attached to the spark plugs located on the engine’s cylinder head, so they are usually easy to find.  

Spark plugs may also experience corrosion or carbon build-up, especially if your vehicle has a burnt valve seal. Valve stem seals, for example, help moderate the amount of oil on the valve stem. When these are defective or experience damage, they can cause carbon buildup on the spark plugs, creating a significant hazard for you and your family. Regularly inspect your car’s spark plugs to identify damage before it’s too late. 

2. The Engine is Idling Rough

Another sign of bad spark plugs or wires is if the car is idling rough. Ideally, the car should be smooth and steady when idling, but the engine may develop a rough idle if the spark plugs or wires are bad. A rough idle is characterized by shaking, bouncing, or vibrating sensations and is one of the most common symptoms of bad spark plug wires. 

3. Engine Hesitation

Engine hesitation is one of the most noticeable symptoms of bad spark plugs and wires and a common engine problem.

Your car should smoothly accelerate once you apply pressure to the gas pedal. But the engine may hesitate or hiccup during acceleration if it’s not getting a steady flow of electricity due to faulty spark plug wires. Further, if your spark plugs are defective, corroded, or damaged, they may not correctly transmit the spark, thus creating engine hesitations. 

4. Engine Misfiring

A car engine converts gasoline into energy that is used to power the vehicle in a process known as internal combustion. Bad spark plug wires can interfere with the electrical current flowing to the engine, making it difficult for the engine to complete the combustion cycle. An incomplete combustion cycle can cause an engine to misfire, which means your car may jerk, stumble, or briefly lose power. A misfiring engine is one of the most alarming and startling symptoms of bad spark plug wires.

What Should I Do If My Car Is Showing Symptoms of Bad Spark Plug Wires?

If your vehicle exhibits one or more of these symptoms of bad spark plugs and wires, it’s likely in need of repair. First, conduct research to determine if you are entitled to free repairs under a vehicle recall. The manufacturer may have issued a recall due to faulty spark plug wires or defective spark plugs.

If there is no recall, look into your state’s lemon laws. These laws protect consumers who have purchased new or used vehicles with defects. Consumers who unknowingly bought a “lemon” have the right to return it to the dealership for a full refund or replacement vehicle.

But is a car with bad spark plug wires considered a lemon? It depends. Even if you believe your car is a lemon, it’s essential to take it in for repairs a certain number of times to ensure you qualify under the applicable lemon laws. The number of repair attempts you need to make depends on the issues you are experiencing and the laws in your state. 

For example, Pennsylvania requires manufacturers to repair a nonconformity that substantially impairs the use, value, or safety of a newly purchased or leased motor vehicle. The consumer must attempt the first repair within one year of receiving the vehicle or before they have driven the car 12,000 miles. 

On the other hand, New York law is more specific about the number of repairs a consumer must attempt to repair the vehicle at least four times and meet other requirements. That said, New York allows consumers to pursue lemon law claims regardless of whether the car is new or used, as long as it was purchased or leased from a licensed dealership.

Can the Manufacturer be Liable for Bad Spark Plugs?

Your vehicle’s manufacturer may be liable for the cost to repair or replace spark plugs or owe you other compensation if the spark plug issue is due to a defect that substantially impacts the vehicle’s use, value, or safety. Additionally, some laws are restrictive in the types of car problems it covers, whereas other states have more expansive laws. 

States vary on what cars and circumstances qualify under the applicable lemon laws. Further, other laws, such as the federal Magnuson-Moss Warranty Act, may apply to the situation and entitle you to receive compensation. 

A lemon law lawyer can help you by investigating your claim and assessing whether you may be entitled to compensation under state or federal laws. Even minor car problems may qualify under current laws, so it is a good idea to consult an experienced attorney knowledgeable in lemon laws to help you protect and assert your legal rights. 

Are Spark Plugs in Used Cars Covered by Lemon Laws?

Lemon laws for used cars vary from state to state in terms of what types of defects and components they cover. For example, the used car lemon law in New York explicitly covers the ignition system, which includes spark plugs and wires. Your car may be protected by New York’s used car lemon law if it meets the other conditions. New Jersey has a used car lemon law but does not explicitly state that spark plug wires are covered. Pennsylvania does not have a used car lemon law.

What Makes a Defect Substantial Under the Lemon Laws?

The lemon laws in Pennsylvania, New York, and New Jersey state that defects are only covered if they “substantially impair the use, value, or safety of the vehicle.” In short, the presence of a defect is not enough to hold the manufacturer liable under the lemon law. If the defect is not significant in nature, the lemon law may not apply.


If you cannot prove that the faulty spark plugs or wires impair the vehicle, you may not be able to hold the manufacturer liable. As the New Jersey Lemon Law Unit explains, lemon laws may apply if the vehicle threatens your or your family’s safety or health or requires excessive repairs. A car is not a lemon if its problems are due to vandalism, a car accident, neglect, or abuse by the consumer.

 These laws are complex, so it’s best to speak to an attorney to determine whether you are protected by your state’s lemon law. If the lemon laws do not apply, the federal Magnuson-Moss Warranty Act may provide protection.

Questions About the Signs of Bad Spark Plug Wires?

The dedicated team of lemon law attorneys at Robison Lemon Law Group is available to answer your questions about the signs and symptoms of bad spark plugs and wires. 

Emma Robison takes pride in providing diligent and tireless advocacy on behalf of consumers. She began her career by helping individuals recover compensation under Social Security Disability and workers’ compensation laws. She continued on that journey to help impact the lives of everyday people by assisting consumers in pursuing justice in the face of big-ticket car manufacturers. 

Now, Emma solely focuses her practice on representing consumers who purchased dangerous or defective vehicles. Clients appreciate her thoroughness, professionalism, clarity, and results. Further, they praise her for listening to their complaints, which many money-hungry dealerships and manufacturers tend not to do. 

To schedule a free consultation, contact us today via email or call us at 844-291-4377. Emma and her team do not charge legal fees to handle or evaluate lemon law claims.

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