1. Park your vehicle on a level surface and turn off the engine. Allow the engine to cool down completely.
2. Open the hood of your vehicle.
3. Locate the spark plugs. The spark plugs on a 2002 Subaru Impreza 2.5L are located on the top of the engine, near the front of the vehicle. There are four spark plugs in total, one for each cylinder.
4. Remove the spark plug wires. To remove a spark plug wire, simply grasp the boot of the wire and pull it straight up.
5. Use a spark plug wrench to loosen the spark plugs. Be careful not to drop the spark plugs into the engine.
6. Remove the old spark plugs.
7. Inspect the old spark plugs. If the spark plugs are worn or damaged, they will need to be replaced.
8. Apply a small amount of anti-seize to the threads of the new spark plugs.
9. Install the new spark plugs. Hand-tighten the spark plugs until they are snug, then use a spark plug wrench to tighten them an additional 1/4 turn.
10. Reinstall the spark plug wires. Make sure the spark plug wires are properly seated on the spark plugs.
11. Close the hood of your vehicle.
