Replacing the spark plugs on your BMW E90 is part of routine maintenance. BMW recommends replacing the spark plugs on E90 normally-aspirated models every 100,000 miles and turbocharged models every 45,000 miles. With all the major engine design changes over the years, spark plugs now last up to three times as long as they did in years past. This is good and bad. It means you save money and time not having to service them so frequently, but run the risk of a spark plug seizing in the cylinder head. I suggest replacing your spark plugs every three years regardless of mileage. If the last time they were serviced is unknown, replace them right away.
BMW E90 models utilize an individual ignition coil for each spark plug, referred to as coil over plug. (green arrows) The coil is a new design used in late model E46 and all E90 models, referred to as pencil ignition coils. This style coil no longer uses fasteners to hold it down in cylinder head, instead using a friction fit. When servicing your spark plugs, be sure the engine is cool and leave yourself about an hour to do the job. Be careful not to drop a spark plug, if you do, replace it. The spark plug insulator can crack and can lead to an engine misfire. Remove engine cover on cylinder head. See our tech article on engine cover removing.
Remove ignition coil from cylinder head by pulling straight up. If coil resists, twist when pulling up to break free from spark plug. The ignition coil rubber boot can become stuck to spark plug over time.
You can also use a flathead screwdriver to lever coil up and out of cylinder head. Be very careful using this method as coil is made of plastic and easily damages. If you find engine oil has contaminated the ignition coil boot you will have to repair the oil leak and replace ignition coil. The source of the oil leak will likely be the valve cover gasket.
Using a 5/8 thin-wall spark plug socket on a 12” extension, remove spark plug from cylinder head. If your spark plug does not fit into spark plug hole, you can remove the ignition coil insulator from valve cover. Use 90° tip snap ring pliers to grab insulator holes and squeeze, then pull insulator up and out of cylinder head. This is for vehicles with plastic valve covers only.
Turbo-charged models require a special spark plug socket. The spark plug requires a 12 point socket available through Pelican Parts, part# XXXXX (BMW part# 83 30 0 495 560) Lightly lubricate new spark plugs with copper based anti-seize. Thread spark plugs into cylinder head by hand, this will prevent accidental cross-threading. Torque spark plugs to 23 Nm (18 ft-lb). Reinstall ignition coils and reconnect electrical connectors. Be sure to route wiring harness as it was before and connect ignition coil grounds. Install engine covers and check your work.