Replacing the Air Filter and Spark Plugs of a Smart 453

To replace the air filter and spark plugs on a Smart, you need to obtain the replacement parts: NGK spark plugs from Amazon with code B01BLN7B0G at a price of £27.00 for the 3-piece kit, and the Mann filter also from Amazon with code B0BGSYBZNX at a price of £13.96; free delivery for both parts.

Start by removing the engine cover: the ignition coils above the spark plugs are on the right, while the filter is on the left.

Starting with the spark plugs, disconnect the coil leads and loosen the 3 screws of 8 mm that secure each coil. For better access, you can unfasten the intake hose, then remove the coils, numbering them to ensure they are replaced in the same position.

Clean the area around the spark plug to prevent dirt from falling into the cylinder; replace the spark plugs one at a time: after removing the old one, immediately screw in the new one, then tighten them all with a torque wrench to 23 Nm. Refit the coils in their respective wells, hand-tighten the securing screws, and then tighten them to 10 Nm. Reconnect the leads and move on to replacing the air filter.

Remove the three screws securing the filter cover, and replace the old one with the new, after cleaning the housing.

Ensure the seal is positioned correctly; then reposition the cover and secure it with its screws, reattach the air hose, and remount the engine cover.