Always follow the spark plug service intervals shown in your owner's manual to figure out when to replace spark plugs. But if you can't remember when you last changed your spark plugs, you can pull them and check the gap and their condition. Once you've put in the labor to begin checking spark plugs, however, you might as well change them and establish a new baseline for the future.

Step 1. Open up and clean your work area.

Step 2. Remove the ignition coil and/or boot.

Step 3. Unscrew the old plugs.

Step 4. Gap all plugs before installing them.

Step 5. Install the new spark plug.

Step 6. Lube, reinstall and fire up.