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Spark Plugs: What are They and When to Replace Them?

It’s really surprising that one of the most important parts of your car is also one of the smallest parts of your car. When worrying about making sure a car can run, most people check the gas, the tire pressure, or the car battery, but no one thinks about the spark plugs.


What Are Spark Plugs and What Do They Do?

Spark plugs are the reason your car starts when you turn on the ignition. These small devices take electricity on one end and create a spark that sets off the combustion process which ignites your car’s engine and sets it in motion.

Without spark plugs, your car won’t start. The health of your spark plugs is directly related to the health of your car’s engine. It’s essential that you keep the spark plugs in good health and replace them as needed so that your car can continue to run at maximum health.

Person holding spark plug


How to Fix Spark-Plug Related Engine DTC Codes?

A faulty spark plug may cause a list of related Diagnostic Trouble Codes in your car and turn on the Check Engine Light. Some of the most common related DTC codes would be P0300-P0312, which indicate there are specific cylinders are experiencing misfires. Check out the video below to see how to fix the faulty spark plug to troubleshoot P0300:

How to Fix P0300 Engine Code in 3 Minutes [2 DIY Methods / Only $4.53]


More videos of spark-plug related DTC codes:

P0301 - Cylinder 1 Misfire Detected

P0302 - Cylinder 2 Misfire Detected

P0303 - Cylinder 3 Misfire Detected

P0304 - Cylinder 4 Misfire Detected

P0305 -  Cylinder 5 Misfire Detected

All videos are produced by nonda Auto DIY Center. Check out their YouTube channel to learn more about DTC codes. 


Why Should You Replace the Spark Plugs?

Over time, spark plugs will age. They are doing a lot of work to use electricity to create bursts of energy that allow your car to start. There are several things that can happen to your spark plugs:

Build up

Air flows through the engine from speed as well as debris and sometimes oil can enter the combustion chamber leading to problems with the spark plugs. These can cause deposits to form on spark plugs and that build up can lead to pre-ignition of the car (before the spark plug has a chance to spark and ignite the engine).

Wear and Tear

Spark plugs are exposed to lots of elements, but as with anything with your vehicle, they’ll eventually lose their effectiveness. Spark plugs last anywhere from 10,000 to 20,000 miles, while more expensive ones can last 60,000 or more miles.


If the cooling system in your engine isn’t functioning properly, your engine will run hot. This can also cause the spark plugs to overheat and reduce their effectiveness.

When you replace your spark plugs, you can be sure that your car will be starting properly. Gone will be the days of jerky, erratic starts to your vehicle and you’ll get a smooth, energetic start.


Signs to Change Your Spark Plugs

If you’re not sure what to look for, it might not be easy to look at a spark plug and recognize that it needs to be fixed. However, there are a few signs that you’ll notice as you drive that can help you recognize when you need to take your car in for maintenance.  

High Fuel Consumption

If you leave a poor-performing spark plug in your car, you could see your fuel efficiency drop by as much as 30%. No one likes having to get gas more often. Each trip to the gas station means more money than you’re spending on your car. If you notice that you’re filling your car more often than usual, you should get your spark plugs changed.

Engine Misfires

Have you ever had your vehicle halt for a fraction of a second and then continue with its usual movement? That’s when your engine has misfired. It can lead to higher amounts of emissions. You should take a look at your spark plugs and see if they can be replaced.

Slow Acceleration

Is your car not accelerating like it used to? Maybe your foot is almost to the floor and your vehicle is trying really hard to push itself up to speed. This sluggishness can be resolved with a spark plug change.

Trouble Starting Your Car

Many people believe that their car not starting is a symptom of a drained battery, but it can also be a symptom of bad or worn spark plugs. If you’ve noticed your car isn’t starting as easily as before, you should have your battery and spark plugs changed as soon as possible.



Replacing spark plugs is not as complex as you think, but monitoring the vehicle and know when to do it is not as simple. You have to care for the vehicle when driving, do regular maintenance and car diagnostic tests, etc.

A simple DIY suggestion is that you get a FREE Bluetooth obd2 scanner and it will help you check your car regularly. Additionally, our product provides other functionalities with our ZUS APP, such as car finder, battery check, mileage tracking, etc. Feel free to claim your free Vehicle Health Monitor and know what's behind the naughty Check Engine Light! 

obd2 scanner

I hope the article above provides you with basic information about the spark plugs. Have you changed a spark plug? What did you do about it? What do you think is the most important part of the process? Please feel free to comment below and join the conversation!


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