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Symptoms of Bad Spark Plugs

Effects of Failing Spark Plugs


For optimum performance, your engine’s spark plugs should be clean with no damage to the electrodes. If your spark plugs become dirty or fouled, it can affect how your engine runs. A fouled or bad spark plug is a plug that has become covered with a substance like oil, fuel or carbon or one that is blistered from running too hot. Driving with fouled or bad spark plugs can cause a host of problems for your engine. Symptoms of bad spark plugs can include:

  • Reduced gas mileage
  • Lack of acceleration
  • Hard starts
  • Engine misfires
  • Rough idling

Reduced gas mileage


Making more trips to the gas station? A sudden drop in fuel economy can be traced to dirty or fouled spark plugs. If the spark plugs aren’t functioning properly, it can have a negative impact on your gas mileage.

Lack of acceleration


If your vehicle has lost its get-up-and-go, bad spark plugs could be the culprit. When a spark plug becomes fouled or dirty, it doesn’t spark effectively which can cause your car to perform sluggishly.

Hard starts


Having trouble starting your vehicle? While your first thought may be a dead battery or an empty gas tank, bad spark plugs could be the cause. You won’t be going anywhere if your spark plugs can’t produce the spark to start the combustion process.

Engine misfires


An engine that hesitates or misfires instead of running smoothly may be attributed to faulty spark plugs. If the combustion process is interrupted, even for a moment, it can cause the performance of your engine to suffer.

Rough idling


When your spark plugs are performing as they should, your engine sounds smooth and steady. A fouled spark plug causes your engine to sound rough while idling. You might also feel the vehicle vibrating.

Next steps

If your vehicle is experiencing any of these issues, a trip to your trusted mechanic is in order. Most problems that are a result of a bad spark plug are relatively easy to fix. However, continuing to drive with fouled or dirty spark plugs can lead to more serious problems that are more costly to resolve.


Learn more about quality spark plugs, find your car part, or find where to buy your auto part today.

The content contained in this article is for informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.

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