Private First Class
Drives: 08 M3 Coupe
Join Date: Jul 2010
DIY - Spark Plug Change - 2008 E92 M3
DIY: Spark Plug Change
Mad Props – ELP_JC for the plenum removal steps that helped me get started. I’ve added a few extra comments in addition to his DIY.
Spark Plugs from Dealer – 24.50 each (8x). I'll look up the part number...
10mm Socket + 2 Extensions
Torx screw driver (T25) to remove air intake box.
BMW Coil Pack Removal Tool – I didn’t have this, so I’ll explain an alternative method.
Adjustable Plyer with narrow teeth profile
Flat Head Screw Driver.
Long automotive magnet to assemble socket set for spark plug #8
Mechanics Gloves – MUST
12 Pack of Beer - MUST
Here's the procedure to remove the plenum (installation is in reverse order):
1. Remove air filter cover (8 T25 screws that don't come off the lid -nice). Wiggle the sucker out. There're DIY for air filter replacements if you can't do it, but I wouldn't continue if you have difficulty removing that cover.
2. Remove the 2 10mm bolts that secure the bottom of the air filter housing and just pull sucker out.
3. Dislodge passenger's side sparkplug cover by giving it a yank on both ends. It is attached by 2 grommits. Once loose, you'll have to remove the 2 10mm bolts holding the coolant reservoir in place, push it to the front to dislodge it from the green grommet on the wheel well, and wiggle both (one with each hand) until you can remove the cover.
4. Remove driver's side sparkplug cover. It dislodges in the same manner as passenger side, but comes out much easier as there is more clearance. Just dislodge fuel hose from the top, and wiggle it under the hose.
CAUTION: Plastic clamps are easily broken, proceed with care.
5. Remove a plastic hose connected to the small piece between the plastic elbow and air filter housing; it has a manual clamp so piece of cake.
6. Remove plenum connector by the oil cap. The PCV valve connection is to the right of the oil cap, you can remove the metal latch and then pull down on the wire to remove it from the plenum.
7. Loosen up all 8 TB (throttle body) clamps with either a long screwdriver or a 6mm socket with extensions.
8. Push the plenum up to break it loose from the TBs. It will be on there tight, use a lot of force. Give it a few good yanks you will feel it break free.
CAUTION: Plastic clamps are easily broken, proceed with care.
9. Once loose (it's easier), you need to disconnect another TWO hoses UNDER the plenum, both with manual clamps as well: a small one is in the front, below the 'snake' going to the air filter, and the big one at the rear, on the driver's side, where the brake booster should be. The manual clamps require pressure on each side to release the teeth holding it onto its connection point.
10. Now the plenum will come out.
Spark Plug Replacement –
General Tips: Start with the Drivers side bank, it has more room to work with, and allow for trial and error for removing the coil packs. BMW also has a special tool for removing the coil packs, I didn’t know this at the time, so I used the ghetto mechanic way. Also, all the plugs were tightened 1 quarter turn beyond “hand tight”. A lot of people recommend to lubricate the treads for easy removal in the future.
1. Remove the electrical connectors from the 4 sparkplugs on the drivers side, will give you more clearance to the coil pack.
2. Once the connectors are out of the way, use an adjustable plyer with narrow teeth profile and adjustable jaw. Something like you would use for a plumbers wrench. The trick is to slide the plyer as far around the coilpack as possible, while using a flat head screw driver lodged under the connector part of the coil pack. With a couple of swift tugs from both the plyer and flat head screw driver, the coil pack will pop off the spark plug AND the cylinder head. These suckers are on there tight. It will take some trial and error to get a feel for it.
3. Once the coil packs are removed, a standard spark plug deep socket is required to remove the spark plug. Have at it!
4. Spark plug #4 on the drivers side will pose your first “cramped” experience trying to remove it. There is very little room, and hoses fighting with you. You may have to assemble the ratchet + extension in pieces with the clearances involved.
5. Your half way there! After the spark plugs have been changed out on the drivers side, make sure each coil pack is properly seated. You need to push down on them very hard and you will hear a “click” sound as it grabs onto the spark plug. A lot of force is required as it connects to both the spark plug and the head of the engine. Connect the electrical connectors to coil packs 1-4, and tuck in the wiring as it originally was (self explanatory once you’ve seen it).
6. Start with the passenger side, same process. Remove the electrical connectors from the coil packs. Untuck the wiring harness to give more clearance to work with.
7. Remove coil packs with the same process of Plyer + screw driver method, one by one. The most difficult one will be spark plug #7 & #8 on the passenger side (2 closest to the back of the engine bay). Coil pack #8 is a complete bitch to snake out once its broken free. Push on the hoses as much as possible and find a path of least resistance, its tight.
8. Start with spark plug 8 removal. You will need to assemble the ratchet + extension + spark plug socket in pieces. There is literally a few inches to work with. Drop the spark plug socket into the cylinder, snake the extension and clip it into the socket, and finally attach the ratchet. Once you feel the spark plug is loose, de-attach the ratchet, yank out the extension (I used a small flathead screwdriver to dislodge it from the extension), and finally use your long magnet to reel the bastard out. Installing the new plug will be done in the same fashion. Drop the sparkplug + socket into the cylinder, attach the ratchet extension, then attach the ratchet. Once the plug is in tight, same process, disassemble the ratchet + extension and use the magnet to pull out the socket.
9. Congrats, the hard part is over. Hit the rest of the sparkplugs on the passanger side. There is more room to work with and its abit less tedious.
10. Make sure the coil packs are properly seated give lots of pressure until you hear the “click” as it attaches to the spark plug.
11. Attach the electrical connectors back to the coil packs. Tuck the wiring harness back into the grooves underneath the coil packs.
12. Replace the spark plug covers on both sides, and re-attach the coolant reservoir with the 2x10mm bolts.
When remounting the intake plenum. Make sure all 8 worm clamps are completely loose. Apply pressure evenly starting from the back until you hear the plenum “click” into place. I had a hard time reinstalling the plenum as it would keep popping out of the throttle bodies. It might help to have 2 people to place pressure on both sides until it snaps into place.
Make sure all the hoses are connected, re-attach all the air intake components, and fire up the beast!
My plugs were fouled up after 54k kms. Unfortunately the car is parked until April when the snow melts. I let the car run for 20+ minutes to see if any codes popped up, was good to go! I’ll update the gas mileage improvement (if any) in the spring. Some may ask why I did this myself... My car is imported from the USA, the BMW does not cover free maintenance program with imports in Canada.
Its my first DIY, be nice!!! Feedback appreciated. Any questions you can ask away, or PM me.