In addition to igniting the air/fuel mixture, the spark plugs in your engine can also serve as useful diagnostic tools. Once removed, compare your spark plugs with the samples illustrated in this section. Typical plug conditions are shown along with their causes and remedies. Most plugs which exhibit only normal wear and deposits can be cleaned, regapped, and installed. However, it is a good practice to replace them at every tune-up.
On some later models, Volkswagen installs Bosch Platinum spark plugs at the factory. These have a center electrode made of platinum wire that is completely sheathed in porcelain. The grounding electrode usually does not wear away as on standard spark plugs and its hard to tell when they are worn. Even though they tend to be more expensive, these and other platinum spark plugs are designed to last at least 30,000 miles (48,000 km). If these plugs are replaced with standard spark plugs, keep in mind that they will not last as long.
REMOVAL, INSPECTION & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6 and 7
The cylinder head is aluminum, which is easily damaged and whose threads are easily stripped. Remove plugs only when the engine is cold.
- If compressed air is available, blow any dirt off the cylinder head where the spark plugs seat.
- On 16-valve engines, pull straight up on the plastic loop attached to one of the spark plug wires. Remove the loop and use it to pull off the remaining wires.
- On 8-valve engines, disconnect the plug wires by grasping the boot or metal shield, don't pull on the wire. Mark the cylinder number on the boot.
- Remove the plugs with a spark plug socket and extension. If removal is difficult, loosen the plug slightly and drip a some penetrating oil onto the threads. Allow the oil time to work, then unscrew the plug. This will help prevent thread damage in the cylinder head. Examine each spark plug.
- If the same plugs are to be installed again, clean them.
- Check and adjust the gap. This includes both old and new spark plugs. Never rely on "pre-gapped" plugs.
- When installing a steel spark plug into an aluminum cylinder head, apply a drop of oil to the plug threads. This can help prevent the dissimilar metals from seizing, which would damage the head next time the plugs are removed. Make sure no oil gets on the electrode or porcelain.
- Torque the spark plugs to 15 ft. lbs. (20 Nm). Do not overtighten or the threads in the head will be damaged.
- Reconnect the wires in the correct order.