Tools You'll Need:
* Spark plug socket: A deep well socket, ideally a magnetic one, sized for your spark plugs (usually 5/8" or 16mm). A flexible extension will be very helpful.
* Wrench: To remove the coil packs. The size will depend on your car; check your manual.
* Ratchet: To turn the socket.
* Torque wrench: Absolutely essential to tighten the plugs to the correct specification.
* Gloves: To keep your hands clean.
* New spark plugs: Make sure you get the correct type and heat range for your engine. Your owner's manual or a parts store can help with this.
* Penetrating oil (optional but recommended): Helps loosen stuck plugs.
* Shop rags or paper towels: For cleaning.
* Jack and jack stands: To safely lift the vehicle. Never work under a vehicle supported only by a jack.
* Wheel chocks: To secure the vehicle.
Procedure:
1. Safety First: Park the vehicle on a level surface, engage the parking brake, and use wheel chocks. Disconnect the negative terminal of your battery.
2. Access the Engine: Raise the vehicle using the jack and secure it on jack stands. Locate the spark plugs. On the H6, they are arranged in two banks, three on each side of the engine. Access may be somewhat tight.
3. Remove the Coil Packs: Locate the coil packs (one per plug). Use the correct size wrench to carefully remove the bolts holding each coil pack in place. Gently lift the coil pack straight up. Take note of the location of each coil pack to ensure you put them back in the correct place.
4. Remove the Spark Plugs: Spray penetrating oil onto the spark plugs if they haven't been changed recently (wait a few minutes). Use the spark plug socket and ratchet to carefully remove each spark plug. Be extremely careful not to drop anything into the cylinder.
5. Inspect the Old Plugs: Check the condition of the old spark plugs. Their condition can provide insights into the engine's health.
6. Install the New Spark Plugs: Carefully install the new spark plugs by hand, screwing them in until they are snug. Then, use the spark plug socket and torque wrench to tighten them to the manufacturer's specified torque. Do not overtighten.
7. Reinstall the Coil Packs: Carefully place the coil packs back into their positions, ensuring they are properly seated. Reattach the bolts and tighten them to the manufacturer's torque specification.
8. Reconnect the Battery: Reconnect the negative battery terminal.
9. Lower the Vehicle: Carefully lower the vehicle using the jack.
10. Test Drive: Start the vehicle and take it for a test drive to ensure everything is working properly.
Important Considerations:
* Gap: While many modern plugs come pre-gapped, double-check the gap specification in your owner's manual and adjust if necessary using a spark plug gapping tool.
* Torque: This is crucial. Over-tightening can damage the threads in the cylinder head, while under-tightening can lead to misfires.
* Accessibility: The tight space around the H6 engine can make this job challenging. A flexible extension on your ratchet will be a huge help. You may also need to use a mirror to help you see the plugs and coil packs.
This is a complex job. If you are not comfortable performing this work yourself, it's best to take your vehicle to a qualified mechanic. Improperly installed spark plugs can lead to serious engine damage.
