How to change spark plugs

Quick insights

• Changing spark plugs is an important part of vehicle maintenance that can help ensure proper engine performance.
• Knowing when and how to change a spark plug can save you time and money.
• Recognizing the signs that spark plugs need to be changed can prevent engine damage and improve fuel efficiency.

Spark plugs might be small, but they play a big role in keeping your vehicle running smoothly. Whether you're a seasoned do-it-yourself-er or a novice looking to understand more about car maintenance, this guide will help you navigate the ins and outs of spark plug replacement.

Why do you need to change spark plugs?

Spark plugs are necessary for your vehicle's engine to function properly. They ignite the air-fuel mixture in the engine's combustion chamber, which provides the force needed to move the pistons. Pistons are cylindrical components that move up and down within the engine's cylinders. They convert the force from the ignited air-fuel mixture into mechanical energy that powers the vehicle.

Over time, spark plugs can wear out or become "fouled," a term that refers to the accumulation of oil, fuel or carbon deposits on the spark plug. A fouled spark plug can lead to poor engine performance, reduced fuel efficiency and increased emissions. Regularly changing your spark plugs can help maintain healthy engine performance and prolong the life of your engine.

Tools needed to change spark plugs

Changing a spark plug requires specific tools and comes with certain costs. Here's what you need to know:

• Spark plug: This is the essential component that needs to be replaced. It's responsible for igniting the air-fuel mixture in the engine's combustion chamber. Spark plug cost can vary widely, depending on if they are basic copper plugs or high-performance iridium plugs. The type of spark plug you need will depend on your vehicle's specifications.
• Ratchet: This is a type of wrench that allows for continuous motion in one direction, making it easier to tighten or loosen the spark plug.
• Spark plug socket: This is a special type of socket designed to fit spark plugs. It has a rubber insert that protects the plug from damage.
• Spark plug gap tool: This tool is used to measure and adjust the distance between the center and side electrodes of the spark plug, ensuring optimal performance.
• Torque wrench: This tool is used to apply a specific amount of force when tightening the spark plug, preventing over-tightening that could damage the engine.
• Extension bar (if necessary): Some vehicles may require an extension bar to reach the spark plugs if they are located deep within the engine.

How to change a spark plug

Changing a spark plug is a process that requires careful attention to detail. By following the correct steps and using the right tools, you can ensure your engine runs smoothly and efficiently:

1. Locate the spark plugs: They are typically found on the engine's cylinder head. In some vehicles, they may be under a cover or hard to reach, so you may need to remove some components, such as the air filter or intake manifold, to access them.
2. Remove the old spark plug: Disconnect the spark plug wire and use a spark plug socket to remove the old plug. Be careful not to pull on the wire itself as this can damage the connection.
3. Inspect the old spark plug: This can give you insights into your engine's condition. For example, deposits on the spark plug can indicate oil or coolant leaks, while a worn electrode could mean the engine is running too hot.
4. Install the new spark plug: Screw it in by hand to avoid cross-threading, then tighten with a socket wrench. Be careful not to overtighten as this can damage the spark plug or the engine.
5. Reconnect the spark plug wire: Make sure it clicks into place. A loose connection can cause the engine to misfire. An engine misfire occurs when one or more cylinders fail to ignite the air-fuel mixture, leading to a loss of power and potentially damaging the engine.

When to change a spark plug

The ideal time to change a spark plug can vary based on the type of spark plug and your vehicle's specifications. As a general rule, traditional copper spark plugs should be changed every 30,000 miles, while platinum or iridium spark plugs can last up to 100,000 miles. However, it's always recommended to check your vehicle's owner's manual for the manufacturer's recommendations.

Recognizing the signs that your spark plugs need to be changed can help you maintain optimal vehicle performance.

Signs spark plugs need to be changed

Here are some indicators that your spark plugs may need changing:

• Poor fuel economy: Worn spark plugs may not ignite the fuel-air mixture in the engine efficiently, leading to higher fuel consumption. If you notice you're filling up the tank more often than usual, it might be time to check the spark plugs.
• Engine misfires or rough idling: This can be caused by a spark plug that isn't firing properly. You might notice the engine sounds different, or the vehicle vibrates more than usual when idle.
• Difficulty starting the vehicle: If your car is hard to start, especially in cold weather, it could be a sign of worn spark plugs. A weak spark can make it harder for the engine to ignite the fuel-air mixture.
• Poor acceleration: If your vehicle doesn't accelerate as smoothly or quickly as it used to, it might be time to check the spark plugs. Worn spark plugs can cause the engine to struggle "under load," a term that refers to the engine working harder, such as during acceleration or when carrying heavy weight.

The bottom line

Changing spark plugs is an important aspect of vehicle maintenance that can significantly impact your car's performance, fuel efficiency and longevity. By understanding why, when and how to change your spark plugs, you can help keep your vehicle running smoothly and potentially avoid costly repairs down the line. Regular spark plug replacement is an investment in your vehicle that can pay off in the long run.