Transform Your Subaru Legacy: A Step-by-Step Guide on How to Change Spark Plugs

Are you experiencing a lack of power or rough idling in your Subaru Legacy? It might be time to replace those aging spark plugs. Replacing your spark plugs is a relatively simple DIY maintenance task that can significantly improve your engine’s performance and fuel efficiency. This guide will walk you through the process of changing spark plugs on your Subaru Legacy, ensuring a smooth and successful experience.

Gathering Your Tools and Supplies

Before diving into the task, ensure you have the necessary tools and supplies readily available. Here’s a comprehensive list:

• New spark plugs: Consult your owner’s manual or a trusted online source to determine the correct spark plug type for your Subaru Legacy model and year.
• Spark plug socket: A 5/8-inch spark plug socket with a rubber insert to prevent damage to the spark plug.
• Socket wrench: A 3/8-inch drive socket wrench that fits the spark plug socket.
• Torque wrench: A torque wrench is crucial for tightening the spark plugs to the correct specifications. The recommended torque for Subaru Legacy spark plugs is typically between 13-15 ft-lbs.
• Extension: An extension bar may be needed to reach the spark plugs in the rear cylinders.
• Ratchet: A ratchet handle to turn the socket wrench.
• Gloves: Protect your hands from grease and grime.
• Safety glasses: Protect your eyes from potential debris.
• Shop towel: For cleaning up any spills or debris.

Locating the Spark Plugs

The spark plugs are located on the top of the engine, typically under the engine cover. The cover is usually held in place by a few clips or screws.

Here’s how to locate the spark plugs:

1. Open the hood: Release the hood latch and prop it open.
2. Remove the engine cover: Locate the clips or screws holding the engine cover in place and remove them. The engine cover will lift off, revealing the spark plugs.

Disconnecting the Ignition Coils

Before removing the spark plugs, you need to disconnect the ignition coils.

Here’s how to do it:

1. Locate the ignition coils: The ignition coils are located directly on top of each spark plug. They are usually black or brown plastic cylinders with a wire connected to them.
2. Unplug the ignition coils: Gently pull the connector off the ignition coil, ensuring a firm grip on the connector and not the wire.

Removing the Old Spark Plugs

Now it’s time to remove the old spark plugs.

Follow these steps:

1. Position the socket: Place the spark plug socket over the spark plug, ensuring it is securely seated.
2. Loosen the spark plug: Using the socket wrench, turn the socket counterclockwise to loosen the spark plug. Be careful not to cross-thread the socket.
3. Remove the spark plug: Once the spark plug is loose, you can remove it by hand.
4. Repeat for each spark plug: Repeat steps 1-3 for each spark plug.

Installing the New Spark Plugs

With the old spark plugs removed, you can now install the new ones.

Here’s the process:

1. Clean the spark plug threads: Use a wire brush or a shop towel to clean the spark plug threads and the spark plug well to ensure a proper seal.
2. Install the new spark plug: Gently screw the new spark plug into the spark plug well by hand until it is snug.
3. Tighten the spark plug: Use the torque wrench to tighten the spark plug to the specified torque. Overtightening can damage the spark plug threads.
4. Repeat for each spark plug: Repeat steps 1-3 for each spark plug.

Reconnecting the Ignition Coils

With the new spark plugs installed, you can reconnect the ignition coils.

Here’s how:

1. Align the connector: Align the connector with the ignition coil.
2. Connect the connector: Gently push the connector onto the ignition coil until it clicks into place.

Replacing the Engine Cover

Once the ignition coils are reconnected, you can replace the engine cover.

Here’s the process:

1. Align the engine cover: Align the engine cover with the engine.
2. Secure the engine cover: Secure the engine cover by replacing the clips or screws.

Starting the Engine and Checking for Leaks

With the spark plugs replaced, start the engine and let it run for a few minutes.

Here’s what to check:

1. Look for leaks: Check for any leaks around the spark plugs. If you see any leaks, tighten the spark plugs again.
2. Listen for any unusual noises: Listen for any unusual noises coming from the engine. If you hear any unusual noises, shut off the engine and inspect the spark plugs.

A Final Check and Enjoy the Improved Performance

After the initial check, you can take your Subaru Legacy for a test drive. You should notice a significant improvement in performance, including smoother acceleration, better fuel economy, and a quieter engine.

Beyond the Basics: Tips for Success

While the steps above provide a comprehensive guide, here are some additional tips to ensure a smooth and successful spark plug replacement:

• Consult your owner’s manual: Always refer to your Subaru Legacy owner’s manual for specific instructions and torque specifications for your vehicle.
• Use high-quality spark plugs: Investing in high-quality spark plugs can ensure optimal performance and longevity.
• Clean the spark plug wells: Before installing the new spark plugs, clean the spark plug wells to prevent dirt and debris from entering the combustion chamber.
• Inspect the ignition wires: While you’re working on the spark plugs, inspect the ignition wires for any signs of damage or wear. Replace them if necessary.
• Check the air filter: A dirty air filter can restrict airflow to the engine, affecting performance. Consider replacing it if it’s dirty.

The Final Touch: Your Subaru Legacy’s New Lease on Life

By following these steps, you can successfully change the spark plugs on your Subaru Legacy, restoring its power and efficiency. Remember to keep a record of the spark plug replacement date for future reference.

Quick Answers to Your FAQs

Q: How often should I change my Subaru Legacy spark plugs?

A: Subaru recommends replacing spark plugs every 30,000-100,000 miles, depending on the model and driving conditions. However, it’s best to refer to your owner’s manual for specific recommendations.

Q: Can I use different types of spark plugs than what’s recommended?

A: It’s not recommended to use different types of spark plugs than what’s specified for your Subaru Legacy. Using the wrong spark plugs can lead to performance issues and even damage to the engine.

Q: What are the signs that my spark plugs need to be replaced?

A: Common signs that your spark plugs need to be replaced include:

• Rough idling: The engine may shake or vibrate when idling.
• Decreased fuel efficiency: You may notice a decrease in gas mileage.
• Misfires: The engine may misfire, causing a rough or jerky acceleration.
• Difficulty starting: The engine may take longer to start or may not start at all.
• Engine hesitation: The engine may hesitate or stumble when accelerating.

Q: Is it difficult to change spark plugs on a Subaru Legacy?

A: Changing spark plugs on a Subaru Legacy is relatively straightforward, even for beginners. With the right tools and a little patience, you can easily complete the task.

Q: Can I change my spark plugs without disconnecting the ignition coils?

A: It’s not recommended to change spark plugs without disconnecting the ignition coils. Doing so can result in a spark and potentially damaging the ignition system.