Is It Time to Change My Spark Plugs?

March 05, 2024
A steering wheel and a car dashboard.

Have you ever tried starting your car and it just stutters? Many assume it’s a faulty battery, but the problem could very well be the spark plugs. This is why it’s so important to keep up with spark plug maintenance and to look out for symptoms of bad spark plugs.

What do spark plugs do?

Using a small bolt of electricity, the spark plug ignites the fuel-air mixture in the engine, which helps your vehicle move. Each spark plug screws into an engine cylinder and connects to the car’s ignition system. [1]

What happens when a spark plug goes bad?

Want to know the signs to look for that can indicate your spark plugs are misfiring? There are a few key symptoms, such as problems with idling, accelerating and fuel economy. We’re going to break down six signs there could be a problem with your spark plugs below. [2]

6 signs of bad spark plugs

1. Irregular upkeep and maintenance

It’s always important to keep up with proper maintenance to ensure a smooth and safe ride. Each car requires a spark plug change at a certain mileage. Check your owner’s manual to see what the mileage is for your vehicle. [1]

2. Rough idling

If you feel excessive shaking or vibrating when your engine is running but not in motion, this is called rough idling. When your spark plugs are misfiring, rough idling may be a symptom. [3]

3. Declining fuel economy

When spark plugs are having trouble producing energy to accelerate your car, more gasoline is used to make up for the bad spark plug. If your vehicle is using more gasoline for starting your car, sitting at a traffic light and driving, your car’s fuel economy is decreasing. [4]

4. Car struggles to start

If your car is just clicking when you try to start it, the cause could be worn-out spark plugs. If the spark plugs can’t produce enough energy to start the combustion process, your car won’t start. Take your car to a professional and have them check out the spark plugs. [1]

5. The engine begins misfiring or pinging

If there is oil on the tip of the spark plug, this can cause the engine to misfire or keep it from starting altogether. It’s important to take your vehicle to a professional if you notice the oil because a repair is necessary. If you don’t repair it, this can damage the catalytic converter, which can be costly to replace. [1]

6. Warning lights come on

If the check engine light comes on in your car, don’t ignore it. This could indicate a problem with the spark plugs or another issue with the engine. Regardless, if the light comes on when you’re driving, you’ll need to find a safe place to pull over and shut off your engine to investigate the issue or take it to a professional to diagnose the issue. [1]

How long do spark plugs last?

Check your vehicle’s owner’s manual to know how long your spark plugs last, because the mileage varies per car. Some spark plugs may last only 18,000 miles, while others last 100,000 miles. Make sure to take your car in for regular maintenance to ensure that it’s running as smoothly and efficiently as possible. Lastly, make sure you and your vehicle are protected with the right insurance. [1]


[1] “How Do I Know If My Spark Plugs Need Replacing?” Chris Hardesty, (accessed Jan 2024).

[2] “How Often to Change Spark Plugs?” (accessed Jan 2024).

[3] “What Causes A Rough Idle In A Car? (11 Reasons + Fixes), (accessed Jan 2024).

[4] “Can Bad Spark Plugs Affect Gas Mileage?” (accessed Jan 2024).


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