The Most Common Symptoms of Bad Spark Plugs

symptoms of bad spark plugs

Spark Plug is a very common item in Spark Ignition Engines. Without a spark plug, there is no way to start the S.I. Engine. So, the importance of a spark plug is known to everyone.

It’s a small item but plays the most important Role to run on the Engine. Sometimes, it can be bigger in size for the Gas Generator or Power Plant Engine. Spark Plug’s main role is to transmit the electric signal from the Ignition coil through high tension lead and finally spark up the combustion chamber’s air-fuel mixer.

The basic symptom of a bad spark plug is you can feel the abnormal behavior of your engine. It may not start or take enough time to start.

Spark Plug is a regular Serviceable component. Just like you change Engine oil, Fuel Filter, Air Cleaner filter from time to time, the same thing goes for the Spark plug. You should replace it in the fixed time period. The time period depends on the model and makers of spark plugs.

Normally, we suggest checking the spark plug when you tune up the car. Check the spark plug gap and color. If the color is almost like burnt, you should change it as soon as possible. We always recommend changing the spark plug after a 20k-30k mile run. Some spark plug can last more. It varies from manufacturer to manufacturer.

If you have a motorcycle, our recommendation is to change from 5000 to 10000 Miles.

If you have a vehicle with Spark Ignition Engine like Car, SUV, trucks or Motorcycles, you should replace the spark plug from time to time. Here we will discuss details about Symptoms of bad spark plugs and how to check spark plugs.

Let’s get going!

Symptoms of bad spark plugs:

01. Fuel Consumption Will Increase:

high fuel consumption cars

When you get better mileage, it means your Fuel is Burning Perfectly and no need to change the spark plug. It’s good in conditions and working correctly. If you feel your car consuming extra petrol or Fuel from the beginning, you should check the spark plug and the gap of the spark plug.

If it’s wrong, compare with the manufacturer standard and adjust the gap. And if your spark plug looks burnt but runs as normal mileage, you should better replace it.

Sometimes, fuel consumption can increase due to other faulty parts like oxygen sensors, air cleaners, fuel filters, or spark plug wire problems.

02. Engine Misfiring

engine misfire symptoms

One of the main reasons for engine misfire is the spark plug problem. When your engine misfire, you can hear engine misfire sound and it’s very embarrassing. Engine misfiring can damage the air cleaner filter and the engine internal components. So, check the spark plug and fix the issue as early as possible.

There are some other causes which may cause engine misfiring. Such as high tension lead, faulty ignition coil plug cap or bad quality fuel. So, what you need to do is you should find out the actual problem and solve the issue as soon as possible. Or else, you’ll put yourself in danger.

03. The car accelerates slowly:

There are so many reasons for your car accelerates slowly. Spark plug issue is one of those cars feels sluggish when accelerating. So many item’s weakness like fuel pump, fuel line, fuel filter, air cleaner, clogged and some sensors issue can make such a type of problem. So, you should confirm by an experienced auto mechanic and solve the problems.

04. Engine Starting Problem:

symptoms of bad spark plugs

Starting problem is a very common problem of your car, motorbike, SUV, Bus and Truck. It will not be started. This can happen in the morning or after a short break or at any of the situation. So many reasons can be there for your car cannot get started like battery problems, starter motor, Electric line’s fault etc.

If you don’t understand what the actual problem is, you must call a certified mechanic for solving the issue. If they confirm it is the spark plug and it requires a change, so do it immediately and use the quality branded spark plug.

We hope you understood the very common symptoms of a bad spark plug. Now, we will discuss the next steps:

Benefits of changing spark plugs:

As a car owner, you should maintain the regular works of your car. If you’re obeying this, your car life will be increased. Besides, fuel and maintenance cost will be minimized.

If you don’t replace the spark plug time to time, it’ll cause damage to your other valuable components of Engine. Spark plug issue interrupts the proper fuel burning. As a result, your car Catalytic converter will be overheated and can get damaged.

How To Tell When You Need New Spark Plugs


Q: What happens when spark plugs go bad?

Ans: You already know the spark plug is the main way to make fuel burning in the combustion chamber. If it goes bad, your car will not start. The fuel consumption will become high. Uneven Sound may come from the engine while trying to start.

Q: How do I know if my spark plugs need changing?

Ans: You can see the manufacturer guideline how much life normally a spark plug has. You can check the color and gaps too. If the color is like burnt, you need to change the spark plug.

Q: What causes spark plugs to go bad fast?

Ans: Bad Fuel and the improper air-fuel ratio will deposit the carbon on the spark plug and it is one of the main reasons for Spark plugs to go bad quickly.

Q: Why do my spark plugs keep getting dirty?

Ans: So many reasons are there to make spark plug dirty. A mixer of air-fuel ratio, spark plug cap, and hard or leaky cylinder valve seal, also improper spark plug gap can make your spark plug dirty.

Q: Can a bad spark plug stop your car from starting?

Ans: Yes, it can. It can stop your car from starting as it sparks up the combustion chamber. Besides, crank position sensor, ignition coil, electric circuit problem can make such a problem too.

Spark Plug Replacement DIY (the Ultimate Guide)


So, these are the basic symptoms of a bad spark plug. We hope that you understood all those and you know very well how to avoid these problems now.

However, if you notice any of these symptoms, change your spark plug as soon as possible or go to your reliable mechanic to solve the issue. Delaying will cause waste of your time and money. If you want to learn more, read other articles on our website. If you have any question, feel free to leave a comment here or contact us.

Happy driving!

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