How to tell if spark plugs need changing?

Spark plugs are a critical component of your vehicle's engine, responsible for igniting the air-fuel mixture and keeping your engine running smoothly. Over time, spark plugs can wear out, leading to decreased engine performance, reduced fuel efficiency, and even engine failure. Knowing when to change your spark plugs can help you avoid these issues and keep your car running at its best.

Signs Your Spark Plugs Need Replacement

• Rough Idling: If your engine is idling roughly or unevenly, it could be a sign that your spark plugs are worn out and not firing properly.


• Decreased Fuel Efficiency: Faulty spark plugs can cause your engine to burn more fuel than necessary, leading to a noticeable drop in your vehicle's fuel economy.


• Difficulty Starting: Worn spark plugs can make it harder for your engine to start, especially in cold weather.li>
  
• Engine Misfiring: If your engine is misfiring or hesitating during acceleration, it could be a sign that one or more of your spark plugs are not functioning correctly.

If you notice any of these symptoms, it's a good idea to have your spark plugs inspected and replaced if necessary.

How to Check Spark Plugs

To check the condition of your spark plugs, you'll need to remove them from the engine and visually inspect them. Look for the following signs of wear:

• Worn Electrodes: The electrodes on the spark plug should be relatively sharp and free of excessive wear. If the electrodes are significantly worn down, it's time to replace the spark plugs.li>
  
• Discoloration: Healthy spark plugs should have a light tan or grayish color. If the plugs are excessively black, oily, or white, it could indicate an issue with the engine or fuel system.


• Cracks or Damage: Inspect the spark plug for any cracks or physical damage, as these can prevent the plug from functioning properly.

If your spark plugs show signs of wear or damage, it's best to replace them with new ones to ensure optimal engine performance and fuel efficiency.

When to Change Spark Plugs

Most vehicle manufacturers recommend changing spark plugs at regular intervals, typically every 30,000 to 100,000 miles, depending on the type of spark plug and the engine. However, it's important to check your owner's manual for the specific recommended replacement interval for your vehicle.

By being proactive and replacing your spark plugs at the recommended intervals, you can help extend the life of your engine and keep your car running at its best.

How often do spark plugs need replacing?

Spark plugs should be changed based on your vehicle's owner's manual, but a general guideline is every 30,000 to 100,000 miles, depending on the type of plug. The most accurate answer is to check your owner's manual, as plug types vary from copper (shorter life) to iridium (longer life) and driving conditions also impact wear. 
General recommendations

• Owner's manual: This is the most reliable source for your specific vehicle. 
• Copper plugs: Typically need replacement every 20,000–30,000 miles. 
• Platinum or Iridium plugs: These are standard in many modern vehicles and can last much longer, sometimes up to 100,000 miles or more. 

Signs your spark plugs may need changing 

• Rough idle: The engine feels shaky, bouncy, or unstable when stopped. 
• Misfiring: A hesitation or jerking sensation when accelerating. 
• Reduced fuel efficiency: You notice a sudden drop in your miles per gallon (MPG). 
• Difficulty starting: The engine cranks for a long time before starting, or takes longer than usual to start. 
• Check Engine light: A steady or flashing "Check Engine" light can indicate a misfire caused by failing spark plugs. 

Factors that can shorten plug life

• Demanding driving habits: Frequent short trips, aggressive acceleration, and driving in extreme temperatures can reduce plug lifespan. 
• Vehicle modifications: Aftermarket engine tuning can require more frequent spark plug changes. 

Does changing spark plugs really make a difference?

Yes--new spark plugs and ignition wires can improve performance, but the size of the gain and whether you'll notice it depends on the condition of the old parts, the vehicle's ignition system, and how ``performance'' is defined. Restore correct spark energy and timing consistency.

How do you tell if a spark plug is bad without removing it?

You can identify a bad spark plug by observing the vehicle's performance, such as a rough idle, difficulty starting, engine misfires, or a lack of acceleration. Additionally, a check engine light may turn on, and you may notice a drop in fuel efficiency. A professional can also test the spark plug's resistance using a multimeter, though this requires removing the plug.
 
You can watch this video to learn how to check spark plug spark without removing the plug: 58sR&R RestorationsYouTube · Apr 26, 2022
Engine performance signs

• Rough idle: The engine may shake or vibrate noticeably when stopped. 
• Difficulty starting: The engine cranks for a longer time or has trouble starting, especially in cold weather. 
• Engine misfires: The engine hesitates, jerks, or stutters while driving. 
• Poor acceleration: The vehicle feels sluggish and slow to respond when you press the gas pedal. 
• Poor fuel economy: You may notice your vehicle's miles per gallon decreasing. 

Dashboard and other signs

• Check Engine Light: This warning light can indicate ignition problems. 
• Engine noises: Listen for knocking or rattling sounds, especially when accelerating. 
• Stumbling or stalling: The engine may stall or stumble at stops or under load. 

How does a car act when spark plugs are bad?

A car with bad spark plugs will exhibit symptoms like rough idling, difficulty starting, poor acceleration, and decreased fuel economy. You might also notice engine misfires, a "check engine" light, or strange engine noises like knocking or rattling.
 
Common symptoms of bad spark plugs

• Rough idling: The engine may shake or feel unsteady, especially when the car is stopped. 
• Difficulty starting: The engine may crank for a longer time before starting, or require the throttle to be depressed. 
• Poor acceleration: The car may feel sluggish or "jerky" when you press the gas pedal. 
• Decreased fuel efficiency: You will likely notice you need to fill up your gas tank more often because the engine is burning fuel inefficiently. 
• Engine misfires: This can feel like an abrupt jerk or stutter and is a clear sign that a spark plug isn't firing correctly. 
• "Check Engine" light: Modern cars can detect a misfire and trigger the "check engine" light, which may be accompanied by a specific misfire code. 
• Engine knocking or rattling: A bad spark plug can cause an unusual knocking sound, particularly during acceleration. 
• Increased emissions: Incomplete combustion from faulty plugs can lead to higher levels of harmful emissions. 

This video explains the symptoms of bad spark plugs: 59shaile car care YouTube · Apr 23, 2023
What to do
If you experience these symptoms, it's important to have your spark plugs checked, especially if they are past the manufacturer's recommended replacement interval. Continued driving with bad spark plugs can lead to further engine damage. 
You can watch this video to learn how to identify bad spark plugs: 58sEasyAutoFixYouTube · Mar 5, 2023