How to Replace BMW 328i Spark Plugs

1. Open the engine hood of the BMW. Turn the plastic knobs that hold the cover on for the cabin filter, which is located in the engine bay just in front of the windshield.
2. Pull the cabin filter out of the filter housing, disconnecting the wire harness for the filter when you remove it. Unscrew the four Torx screws that hold the filter housing to the engine bay. Set the filter housing aside. Wipe any dust out of the filter housing.
3. Remove the plastic covers on the bolts that hold the main engine cover in place. Use a 10-mm socket and ratchet to remove the 10-mm bolts. Set the engine cover aside. To remove the other engine cover, remove the oil cap, then the bolts that hold the engine cover on.
4. Remove the coils that go to the spark plugs. Note which coil goes to which plug with a marker and some tape, or change one plug at a time, so the coils and plugs are not mixed up. Remove the coil by removing the small bolt that holds the coil, and pull the coil off of the plug. Disconnect the wiring harness by pulling the lever up that retains the wiring harness.
5. Remove the spark plug by inserting the spark plug socket in the hole that the plug is located in. Use a 6-inch extension, and insert the socket until you feel it seat on the spark plug. Turn the socket counterclockwise with the ratchet until the plug is loosened from the engine. Remove the plug from the engine carefully so as not to drop it.
6. Gap the new plug according to the plug manufacturer's recommendations with a plug gapping tool. (This will vary depending on the type of plug.) Apply some anti-seize compound to the plug. Insert the spark plug with the plug socket, and tighten it to 30 foot-pounds with a torque wrench.
7. Reinstall the coil and reattach the wiring harness. Reinstall the engine covers, bolt the cabin filter back in place and reinstall the cabin filter and filter cover. Start the vehicle to ensure that the plugs are installed correctly and the engine is running normally.