How to Replace the Spark Plugs on a BMW 328

1. Wait for the engine to cool down if the car has been driven to avoid damaging the threads for the plugs. This will also minimize the chances of burning yourself while you work.
2. Remove the oil filter cap. Remove the round plastic caps on the engine cover by prying them up with a flat head screwdriver. Use a socket and a ratchet to remove the 10 mm nuts under the caps that hold the engine cover in place. Replace the oil filter cap and set the engine covers aside.
3. Pry up the metal clips that hold the wiring harness onto the coils with a flat head screwdriver. Use a socket to remove the 10 mm nuts that hold the coils to the engine. Pull them straight out and set them aside. Keep track of which coil goes where or simply change the plugs one at a time.
4. Clean the holes for the plugs with a clean, dry rag, removing any excess oil and dirt before removing the plugs from the engine. Also clean the areas around the holes. This will prevent anything from falling into the spark plug hole when the plugs are removed.
5. Attach the spark plug wrench to a 6-inch extension so that you can reach the spark plugs. The plug wrench has a rubber insert inside of it that grips the spark plug and prevents it from falling out as the plug is removed. Place the wrench over the plug until you feel it seat onto the plug then turn it counterclockwise to loosen and remove.
6. Gap the new spark plugs with a plug gapping tool according to the manufacturer's recommendations, which will vary depending on the plug. The gapper slides between the tip and the electrode on the plug until it sets the proper distance between them.
7. Insert the plug into the spark plug wrench and hand-thread it into the motor, ensuring that it does not cross-thread. Use a torque wrench to tighten the plugs to 18 foot-pounds. Replace the coils over the plugs. Reinstall the ground straps attached to the studs that the nuts thread onto then tighten the nuts. Refasten the wiring harness with the metal clip.
8. Replace the engine covers, the nuts that hold the covers on and the plastic plugs that go over the nuts. Start the motor to ensure that it is running correctly.