Spark Plug Replacement

E46 BMW 3-series Spark Plug Replacement

Time required: 45 minutes including taking pictures and detailing your engine bay

Materials/tools required

10mm socket, spark plug socket, 6" socket extension, anti-seize compound, 6 spark plugs, T30 Torx driver, torque wrench.
Spark plugs - NGK BKR6EQUP. I believe these are OEM on the M52 and M54 engines (all non-M E46s).

Step 1: Remove cabin microfilter cover. This is done by twisting these three 'knobs' 90 degrees - it then lifts right out.

Step 2: Remove cabin microfilter (it lifts right out) and release wiring harness from microfilter enclosure. This is done by carefully pulling toward you from the bottom then lifting it up.

Step 3: Unscrew the four T30 screws holding the microfilter enclosure in place. The enclosure then pulls right out. Place it aside (not on the engine like shown.

Step 4: This step isn't necessary, but I like to check the condition of the engine at any opportunity. It'll also give me a chance to clean under there. A clean engine is a happy engine. Remove the first (top) plastic engine cover. To do this, use a flat-bladed screwdriver to pull out the two covers... then unscrew the bolts with your 10mm socket. Then lift it right off.

Step 5: Remove the left plastic engine cover. To do this, you'll have to remove the oil cap. You can then pry out the covers and remove the nuts (not bolts this time) with your 10mm socket. Lift the cover right off and place aside, then put your oil cap back on - after all, you wouldn't want to drop anything down there.

Step 6: Prepare your spark plug socket and your 6" extension. Spark plug sockets typically have a rubber washer in them to help "grab" the sparkplug. I read a handy tip that helped out here - wrap electrical tape around the socket and extension to keep them from coming apart when pulling the spark plug out.

Step 7: Here are the coils. In the how-to I had previously linked in the wiki, you had to unbolt the coils. On my car, it's much easier - Pull the edge of the cover up in the direction of the arrow. It rotates up 90 degrees and the wiring plug automatically pops out of it.

The coil then pulls right off and up (don't be afraid to pull hard, it has to "pop" off of the sparkplug:
I changed the spark plugs one at a time, replacing each plugs coil before proceeding to the next one.

Step 8: Place your extension and spark plug socket down into the hole that the coil came out of. Twist it until you can press it down on the spark plug (you'll feel it secure itself). Attach your socket wrench and loosen it - after a turn or so, you'll be able to disconnect your wrench and twist the rest of it out by hand.

Step 9: Put anti-seize compound on the threads of the new plug. I placed some down the threads as seen here, then used a lint-free microfiber towel to coat the threads all around.

Step 10: Place the new spark plug inside your sparkplug socket and place it down in the hole. Twist by hand, then attach a torque wrench and torque down to 30nm. As you can see, I had no problems using my full size torque wrench even on the back socket. Firmly press the coil back onto the plug, then re-attach the wiring harness. To re-attach it, the top coil lever must be completely up in the vertical position. Then, when you snap it back down to the horizontal position, the wiring harness attaches itself firmly.

Step 11: Start car, verify it runs :).