Tools You'll Need:
* New spark plugs: Make sure you get the correct type and heat range for your engine. Your owner's manual will specify this.
* Socket wrench set: You'll need a socket that fits your spark plugs (likely 5/8" or 16mm). A ratchet and extension will also be very helpful.
* Spark plug socket: This is a special socket with a rubber insert to grip the spark plug and prevent damage.
* Torque wrench: Crucial to avoid over-tightening or under-tightening the plugs. Your owner's manual will specify the correct torque.
* Gloves: To protect your hands from grease and dirt.
* Safety glasses: To protect your eyes from debris.
* Possibly a wire brush or compressed air: To clean the plug wells.
* Jack and jack stands: Essential for safely lifting the vehicle. Never work under a vehicle supported only by a jack.
* Wheel chocks: Place these behind the rear wheels to prevent the vehicle from rolling.
* Owners manual: Consult your manual for specific torque specifications and diagrams.
Procedure:
1. Safety First: Park on a level surface, engage the parking brake, and use wheel chocks. Disconnect the negative (-) battery terminal to prevent accidental shorts.
2. Access the Engine: Lift the vehicle using the jack and securely place it on jack stands. Locate the engine bay and the spark plug access points. The location varies slightly depending on your engine, but generally they are on top of the engine, under the coil packs. On a 1998 Subaru Legacy, you'll likely need to remove the intake manifold's top cover. Consult your owner's manual for this specific part.
3. Remove the Coil Packs: Most likely, the ignition coils are held in place with bolts or clips. Carefully remove these to access the spark plugs. Note the position of each coil pack so you can replace them correctly. Take photos if necessary.
4. Remove the Spark Plugs: Use the spark plug socket to carefully remove each spark plug. Avoid dropping the plugs into the cylinder as this can damage your engine.
5. Clean the Plug Wells: Use compressed air or a wire brush to remove any dirt or debris from the spark plug wells. This prevents debris from falling into the cylinder.
6. Install New Spark Plugs: Carefully install the new spark plugs by hand, threading them in gently. Once they are hand-tight, use the spark plug socket and torque wrench to tighten them to the manufacturer's specified torque. Over-tightening can damage the plugs and the threads in the engine block.
7. Reinstall the Coil Packs: Carefully replace the ignition coils, ensuring they are properly seated and secured.
8. Reconnect the Battery: Reconnect the negative (-) battery terminal.
9. Lower the Vehicle: Carefully lower the vehicle using the jack.
10. Start the Engine: Start the engine and listen for any unusual sounds. Check for any leaks around the spark plugs.
Important Considerations:
* Gap: Some spark plugs may need to be gapped to the manufacturer's specifications. Use a spark plug gapping tool if needed. This step is crucial for proper ignition.
* Torque: Using the correct torque is vital. Over-tightening can damage the spark plug threads, while under-tightening can lead to misfires. Your owner's manual will specify the correct torque for your engine.
* Consult your owner's manual: This guide provides general steps; your owner's manual will contain specific details and diagrams relevant to your 1998 Subaru Legacy.
If you're not comfortable performing this task yourself, it's best to take your vehicle to a qualified mechanic. Improperly installed spark plugs can lead to engine damage.
