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What Causes Bad Spark Plugs And It’s 4 Sign Discussed

What Causes Bad Spark Plugs

When your vehicle’s spark plugs suddenly wear out, you wonder what could be the valid reason. Well, there are specific reasons for this. Some are inevitable, while some are evitable and somewhat preventive if you want.

What Causes Bad Spark Plugs

In this article, you will know the causes, symptoms, and preventive measures for worn-out spark plugs. We will also answer some of the most common queries relating to spark plugs.

2 Ways that can prevent spark plugs from going bad:

Ways That Can Prevent Spark Plugs From Going Bad

#1. Constant maintenance:

If you continuously maintain the spark plugs from time to time, you can prevent them from going bad. As the engine uses oil from the combustion chambers, so some oil gets outside of it.

After several uses, you will find spark plugs getting clogged with oil and fuel from the engine. Thus, the spark plugs’ outlook gets worse, and the insulator tip cannot work correctly.

Hence, it would be best if you got the spark plugs checked once in a while. If not you, you can go to any car servicing center.

#2. Timely replacement:

With the old age of your car, the spark plugs also get old. This part is inevitable. You cannot prevent spark plugs from getting bad completely, so they need time-to-time replacement to run your car engine smoothly.

Even if you maintain them well, it might only increase their longevity by a few months but won’t make them last forever.

The plugs don’t cost much, so you should replace them on a routine basis, depending on your vehicle usage. More use of the car wears them out quickly.

How Can I Test My Spark Plugs?

Fortunately, there are several ways to test your spark plugs:

1. Spark plug tester:

The most convenient way to test your spark plugs is to use a spark plug tester. This device clamps onto the spark plug and uses a low-voltage current to check its functionality. If the spark plug tests okay, it’s working properly.

2. Manual testing:

You can also manually test your spark plugs. First, remove the spark plug from the engine, and then examine the electrodes at the end of the spark plug. The gap between the electrodes should be around 0.7-0.8mm, and the electrodes should be free of dirt or carbon buildup. If they seem worn out or damaged, you’ll need to replace them.

3. Visual inspection:

You can also conduct a visual inspection of your spark plugs by inspecting the spark plug wire boot and the spark plug itself. Look for signs of corrosion, metal chips, or other damage. These are all indicators that the spark plugs may be faulty.

What Happens When Spark Plugs Are Bad?

Bad spark plugs are one of the most common causes of vehicle issues. They can cause a wide range of problems, including misfires, rough idle, rough acceleration, reduced gas mileage, and hard starts. 

How Long Do Spark Plugs Last?

The answer typically ranges from 30,000 to 50,000 miles, depending on several factors. To ensure the optimum performance of your vehicle’s engine, it’s essential to change the spark plugs regularly.

Can Spark Plugs Be Cleaned?

The answer is yes, spark plugs can be cleaned and reused. Cleaning spark plugs helps to restore their performance, allowing them to continue to spark and fire more efficiently. Whether you decide to clean your spark plugs or have a mechanic do it, it is important to understand the necessary steps and tools.

What Causes Spark Plugs To Overheat?

There are a few main reasons why spark plugs may overheat, including:

  • Faulty or worn-out spark plugs- Over time, spark plugs wear out and can no longer generate the correct spark to ignite the fuel. To prevent spark plugs from failing and causing other damage to the engine, it’s important to replace them periodically.
  • Incorrect fuel/air mixture – If the air/fuel ratio is incorrect, your spark plugs may be working too hard, causing them to become overly hot.
  • Clogged filters- A clogged air filter can reduce the air going into the engine, making the spark plugs work harder to ignite the air/fuel mixture.
  • Carbon buildup- Carbon deposits caused by fuel burning can reduce the efficiency of a spark plug, resulting in overheating.
  • Loose or faulty wiring- Faulty wiring can cause interference with the power going to the spark plugs, leading to overheating.

Can You Use Wd-40 To Clean Spark Plugs?

WD-40 is one of the most versatile all-purpose cleaners. It’s been around for nearly 70 years and used for many different tasks, from lubricating parts to cleaning surfaces and more. Many people don’t realize that WD-40 can be used to clean spark plugs.

How Can I Improve My Spark Plugs?

It’s simple—they ignite your fuel, get your engine running, and keep it running. When they aren’t functioning properly, your engine won’t run efficiently and could stall. That’s why it’s important to maintain and improve your spark plugs.

Bad Spark Plug Wires Symptoms

Here are some common bad spark plug wires symptoms to look out for:

  1. Engine misfire – The most obvious symptom of bad spark plug wires is engine misfiring, which is when your car’s engine momentarily stalls out or sputters. This symptom often goes hand-in-hand with a decrease in power.
  2. Poor acceleration – Another symptom of bad spark plug wires is a decrease in power when you push down on the accelerator. Your vehicle’s engine should be able to increase speed easily, without strain.
  3. Slow starts – If it takes you longer than usual to get your engine to turn over, it could be a sign that your spark plug wires must be replaced.
  4. Poor fuel economy – Poor fuel economy is another symptom of bad spark plug wires. Faulty wires can cause your engine to run inefficiently, burning more fuel than necessary and making your car less fuel-efficient.
  5. Backfiring – If your car backfires or makes a popping sound when you accelerate, it could be a sign of a malfunctioning spark plug wire.

How Often Should Spark Plugs Be Changed?

Spark plugs should be changed every 30,000 to 50,000 miles. This interval of time will ensure that your spark plugs are performing optimally and are effectively igniting fuel intake for your engine.

4 Signs that show extreme spark plug damage:

Signs That Show Extreme Spark Plug Damage

1. Car engine hesitation:

Your vehicle will also suffer from engine hesitation due to insufficient electrical current flow to the car battery through ‘bad’ spark plugs. For the remedy, replace your spark plugs and see the smoothness in the car.

2. Engine light:

In the engine lightbox, you will see an unusual illuminating light-detecting misfiring engine. That is mostly due to bad spark plugs. If that’s so, visit an expert mechanic, he will help you scan to check the engine’s light.

3. Poor fuel economy:

With bad spark plugs, the combustion cannot be fulfilled completely, so the car’s fuel economy falls. Though there could be other reasons for it, for the initial inspection, you must check the spark plugs.

4. Hard starts:

One of the apparent reasons you might feel like the spark plug has gone wrong, is a hard start. Initially, it may seem like a mere battery failure. But if the battery appears to be okay, then the spark plug is the reason. Get them changed before the entire engine gets hampered.


Importance of spark plug for vehicles:

Importance Of Spark Plug For Vehicles

Spark plugs serve your vehicle’s engine power to run your car. They are the engine’s powerhouse that combines air/ fuel mixture into gas in its combustion chambers, which is then required by the engine to run.

Hence, if the spark plugs wear out, the symptoms will directly show in your car’s performance. If you overlook the signs, then the engine might completely stop working.


Can replace spark plugs offer the same performance?

Yes, spark plugs vary from brand to brand. If you want the same performance as the previous one, it is better to replace it with the same spark plug. To avail the optimum performance for a long time, you have to invest in a high-quality spark plug set.

Are the reasons for wearing out spark plugs the same for every vehicle?

Any vehicle that contains an engine requires spark plugs. And the spark plugs serve the same for every car. Therefore, it is evident that spark plug-wearing symptoms and reasons are the same for everyone.


Now that you know the reasons for spark plugs getting bad, you should start working on keeping your vehicle in good condition. A vehicle without an engine is like a human body without a heart.

And that engine’s power is the spark plugs. Therefore, it is crucial to care for it to have a smooth and safe journey with your dear vehicle.

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