How To Tell A Spark Plug Is Bad

How to Tell a Spark Plug is Bad

If you’re experiencing poor engine performance, one of the first things you should check is your spark plugs. Knowing how to tell a spark plug is bad can save you time and money, as well as prevent further damage to your engine.

Signs of a Bad Spark Plug

There are several signs that indicate a spark plug may be bad:

  • The engine misfires or runs rough
  • The engine won’t start or is hard to start
  • The fuel economy decreases
  • The check engine light comes on
  • There’s a lack of acceleration or power

If you notice any of these signs, it’s important to inspect your spark plugs to determine if they need to be replaced.

How to Inspect Your Spark Plugs

To inspect your spark plugs, you’ll need to remove them from your engine. Here’s how to tell a spark plug is bad during the inspection:

  1. Look for physical damage, such as cracks or chips in the porcelain insulator or electrode
  2. Check for fouling, which is when the spark plug is covered in a black, oily substance
  3. Check the gap between the center electrode and the ground electrode using a feeler gauge
  4. Compare the condition of each spark plug to determine if any are significantly different or worse than the others

If you notice any of these issues, it’s time to replace your spark plugs.

FAQs

Q: How often should I replace my spark plugs?

A: It’s recommended to replace your spark plugs every 30,000 to 100,000 miles, depending on the make and model of your vehicle.

Q: Can I clean my spark plugs instead of replacing them?

A: While you can clean your spark plugs, it’s generally not recommended. Cleaning can damage the delicate electrode and insulator, and it’s often more cost-effective to simply replace them.

Q: How many spark plugs does my engine have?

A: It depends on the make and model of your vehicle. Most engines have either 4, 6, or 8 spark plugs.

Conclusion

Knowing how to tell a spark plug is bad is an important skill for any vehicle owner. By inspecting your spark plugs regularly and replacing them as needed, you can improve your engine’s performance and prevent further damage.