How To Tell If Your Spark Plugs Are Bad

Spark plugs are a crucial component of your vehicle’s engine system. They help ignite the fuel in the combustion chamber and keep your car running smoothly. Over time, spark plugs wear out and need to be replaced. But how do you know if your spark plugs are bad? In this article, we’ll go over some signs that your spark plugs may need to be changed.

Signs that Your Spark Plugs are Bad

1. Rough idling: If your car is idling roughly or stalling, it could be a sign that your spark plugs are worn out. 2. Poor acceleration: If you’re having trouble accelerating or notice a decrease in power when you press down on the gas pedal, it could be due to bad spark plugs. 3. Engine misfires: Misfires occur when the spark plugs fail to ignite the fuel in one or more cylinders. This can cause your engine to run poorly and may even damage your catalytic converter. 4. Poor fuel economy: Worn out spark plugs can cause your engine to run less efficiently, resulting in decreased gas mileage. 5. Difficulty starting your car: If your car is having trouble starting, it could be due to bad spark plugs. 6. Engine warning light: If your engine warning light comes on, it’s a good idea to have your spark plugs checked.

FAQs about Bad Spark Plugs

Q: How often should I replace my spark plugs?

A: It’s recommended that you replace your spark plugs every 30,000 miles or every two years, whichever comes first.

Q: Can bad spark plugs damage my engine?

A: Yes, if left unchecked, bad spark plugs can cause damage to your engine over time.

Q: How much does it cost to replace spark plugs?

A: The cost to replace spark plugs varies depending on the make and model of your vehicle. On average, it can cost anywhere from $100 to $300.

Q: Can I replace my spark plugs myself?

A: If you’re comfortable working on your car, you can replace your spark plugs yourself. However, it’s important to follow the manufacturer’s instructions and use the correct tools.


If you’re experiencing any of the signs listed above, it’s important to have your spark plugs checked. Ignoring bad spark plugs can lead to engine damage and decreased fuel efficiency. By keeping an eye out for these warning signs and replacing your spark plugs as needed, you can ensure that your car runs smoothly and efficiently.