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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 02-10-2012, 04:48 PM   #1
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My Ride: E46 M3
DIY: E46 M3 detailed ignition coil replacement and spark plug replacement

For those that own a Bentley manual, the instruction for this fix is in there but those who dont, my DIY should provide the instructions without the manual. Thanks for viewing and again, thanks to the forum for being a guide for my own DIY.

Tools needed:
3/8" drive ratchet
10mm deep well hex socket
19mm hex socket
5/8" deep well hex socket (16mm deep well hex socket can also be used)
T30 torx bit drive socket
3/8" ratchet extensions
3/8" drive torque wrench
Needle nose pliers
Straight head screwdriver
10mm open end wrench (the OEM one in the toolkit works just great)
Telescopic magnet stick

Parts and supplies needed:
6 x NGK DCPR8EKP spark plugs (PN: 12120022902) or NGK DCPR8EIX Iridium IX spark plugs
6 x Bosch ignition coils (PN: 12131712219)
Rags and paper towels to clean valve cover if oil is present
Small plastic bags to contain screws and bolts
E46 3 series Bentley manual for reference if you have it

Also now is a good time to order any parts that require the engine cover to be disassembled. Parts such as microfilter and any sensors/cables that may be faulty under the engine cover. If need be, the DIY can be continued on to do the valve adjustment and checking the VANOS section since the engine cover is already off.

If youre only interested in replacing one or a few ignition coils, youll need to do the ignition coil test to determine the faulty coils beforehand. This video describes just that.

Step 1: Park car on level surface and pop open hood. Allow the engine bay to cool if you havent already. My car was in limp mode and I had a pretty steep gradient to get up into my buddy's garage, so I had to drive around and warm the car up first. If you are working with a warm engine, I warn you to not touch any of the metallic sections of the engine. Be sure to use caution.

Step 2: Gather all tools needed for the fix. Up above are the tools you will need to perform this DIY. Also gather all your parts needed for the fix. Its easier to perform a car fix when everything is organized and within reach.

Parts you will need for this DIY.

Step 3: If your M3 has a strut tower brace, youll need to remove the middle section of the brace first before continuing. Unclip the plastic wire harness above the engine thats connected to the front of the microfilter. There are 4 clips on this harness. Simply, but gently pry apart the plastic ears. Set the black harness cover to the side. Allow the positive terminal cable and black PVC cable to fall out of clips from inside the harness. You may have to gently pull down on them to remove them. Ive circled the 4 clips in red.

Step 4: Locate the microfilter towards the back of the engine bay and directly above the engine itself. There are 3 retaining clips that are spring-loaded holding the top of the microfilter cover closed. Simply twist 90 degrees to relieve the tension on the spring and push the clips upward. Leave the clips in the cover itself. Remove the cover by pulling up and out. Ive circled their locations in red.

The clips in their "open" postion after they have been twisted.

Step 5: The microfilter is now exposed. Remove it by simply pulling up and out. The two faces of the microfilter are different because of the orientation that they sit within the microfilter housing, but I went ahead and marked the bottom side to note the clean side of the filter.

I simply took a Sharpie marker and wrote bottom on the bottom of the filter even though the filter has one orientation it will fit in. This just makes for quicker reinstallation for first timers.

Step 6: Locate the 4 screws that hold the microfilter housing to the car body. After removing the microfilter, they are quite present. These have T30 hex drive bit heads so take out your wrench and extension if you need one, and slip the drive bit on. Unscrew all 4 screws and bag them. Ive circled their locations in red.

I placed a piece of paper over the hole at the bottom of the housing to prevent the screw from falling down it. This is just a precautionary measure. There is a hole on both ends of the housing.

Bag those screws! This will help prevent loss of valuable and much needed bolts, screws, nuts, etc. It also allows for better organization and will prevent mixing of parts.

Step 7: If you have angel eyes and have hidden the angel eye power wire underneath the rubber seal around the microfilter housing, youll need to remove it. Simply lift up on the rubber seal and pull the wire out. For those that dont have angel eyes, you can skip this step.

Place all your parts that have been removed off to the side and in a neat location.

Your engine bay should look like this by now.

Step 8: Push angle eye power wire up and out of the way. I simply placed mine up and over the cowl to keep it off the engine.

Step 9: Locate and remove the PVC vent tube on top of the engine. It spans from the engine cover over to the intake cover. There are small release clips around the base of each inlet on the hose. Squeeze these tight (youll notice the grip locations for your fingers) and pull up on the hose. Ive circled the grips in red. Set aside for now (you can replace it after the engine cover has been removed).

The vent hose removed and the grips circled in red.

Step 10: As a safety precaution when working with anything electrical, I went ahead and disconnected the negative terminal from the battery. The battery is located in the truck to the right. Lift up on the trunk floor and expose the two plastic rivets holding the battery cover in place. Remove the rivets with a straight head screwdriver. Just a note, if you are going to do a ignition coil test, youll need to have the battery hooked up with power supply to the car.

Step 11: Place a small 10mm open end wrench over the nut holding down the negative battery terminal. Twist off and bag the nut. Simply, but gently pull up on the negative terminal to stop the flow of power to the car. Push terminal down and to the side of the battery. Do not let the two terminals touch (postive and negative).

Placing the wrench on the 10mm nut and removing.

Placing the negative terminal cable down and to the side of the battery.

Step 12: This step is optional but will allow more clearance for this fix. You can still perform the fix with the positive power cable draped over the engine. Locate and remove the positive terminal in the engine bay. It is a small black box with a release clip above the strut tower in front of the DSC module bin. Pop the clip and flip back the cover. There is a large nut holding down the positive power cable. Using the 19mm socket and wrench, remove the nut and bag it. Pull the cable off of the threaded stud and place aside in the engine bay. Be sure to note mentally where you place it. Also, the black PVC cable can be disconnected from the side of the engine but I left it connected as it wasnt an issue with this DIY.

Placing cable off to the side out of the way.

Step 13: Remove the left engine shroud piece. There are 2 plastic rivets. Using needle nose pliers, pull up on the center pins and bag them. Place the shroud aside. This will give you more room to work. Ive circled their locations in red.

The second plastic rivet is directly in front of the VANOS.

The left engine shroud off and out of the way.

Step 14: Remove the oil filler cap on top of the engine cover.

Step 14: Locate the six chrome nuts that hold the engine cover in place. Using a 10mm deep well hex socket and wrench, remove them. Ive circled them in red.

The sixth nut is in the lower corner of the VANOS area. Removing the engine shrould in the previous steps will expose it and provide more space to work.

Step 15: Pull up on the engine cover after removing the 6 nuts and remove it. Carefully place engine cover out of the way where it wont get stepped on.

This is how the engine should look now. You are now looking at the top of the valve cover where the ignition coils sit.

Step 16: Be sure to replace the oil filler cap to prevent dust and contaminants from getting into the engine. You can also replace the PVC vent tube back over its inlet holes.

Step 17: The black plastic wire harness on the low side of the valve cover has two release clips. Simply pinch them together and pull the harness up slightly. Pull up and slide the harness down a little ways towards the side of engine block (nearest headers) to provide more space to reach the igntion coil connections. Dont push the harness too far as this will put stress on the cables clamped to the harness. Ive circled the clips in red.

Unclipping the far clip on the harness.

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Old 02-10-2012, 04:49 PM   #2
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Step 18: Locate the first ignition coil for the first cylinder. There is a release clip on the head of the coil. Flip this clip up. When the clip is flipped, youll notice the cable pushes slightly outward for easier removal.

Step 19: Gripping the head of the ignition cable with one hand and holding the top of the ignition cable still with the other, gently pull the cable out of the ignition coil.

Step 20: Notice the hole in the ignition coil clip. This is used for removal of the ignition coil. You can use your finger to try and pull the coil out, but I found it easier to use a screwdriver to pull it out. Insert the screwdriver through one side of the coil and grip both sides of the screwdriver with your hands. Pull straight up on the coil. It will take some force because of the suction the coil has. Set the coil off to the side.

Here is the igntion coil removed.

Step 21: Now that the first ignition coil is removed, the process is the same for the remaining coils. Run down the cylinder line and flip the clips on the ignition coil heads. Then repeat the previous step and remove each ignition coil. There are 6 total.

All six ignition coils removed.

The valvetrain cover should look like this now after the coils have been removed.

Step 22: Locate the 6 spark plugs at the bottom of the ignition coil cylinders. Using the 5/8" deep well socket, 3/8" ratchet extension, and 3/8" ratchet, loosen each spark plug one at a time. Be sure the socket slips completely over the spark plug to prevent stripping of the head. It will take some force to break the spark plugs loose.

A spark plug located at the bottom of an ignition coil cylinder.

Inserting ratchet and socket over the spark plug.

A closer view of the socket in the clyinder.

Step 23: Use the telescopic magnet stick to remove each spark plug from the cylinders.

All 6 spark plugs layed out with cylinders 1-6 corresponding left to right.

The cylinders are completely empty. This is a chance to clean out any oil or contaminants that may be in the cylinders.

Clean cylinder.

Step 24: Gather up the new spark plugs. Be sure the spark plugs have the right electrode gap distance of 0.032", if not then they will require a gap tool to put them in spec. Disconnect the 3/8" ratchet from the extension. Place a new spark plug in the socket as shown and rub a little anti-seize on the threads. Hand tighten each one into the bottom of the cylinders.

Hand tightening each new spark plug.

Step 25: Pull out the 3/8" torque wrench and set to 22 ft-lbs. Place the extension and socket on the end of the torque wrench. Be sure the wrench is calibrated. Torque each new spark accordingly to the set torque, listen for the click-click as the wrench seats each plug.

Step 26: Pull out the new ignition coils. Seat the plastic protruded head of each coil between the metal indicators circled in red. These will line the coil up with the connection cable. Be sure to push the coil down tight over the spark plug. The last bit of pushing will have a little resistance to it as the coil forms a suction and seals.

Step 27: Reconnect the ignition coil cables to the coils themselves. Once the connection cable heads are fully inserted into the coils, push down on the ignition coil clips. It will pull the remaining slack of the cable in and secure the ignition coil cable.

Step 28: Reclip the black plastic wire harness on to the lower portion of the valvetrain cover. Be sure all 6 coils are seated and reconnected.

Step 29: Reconnect the positive power cable to the positive stud. Remember, the socket for the positive terminal nut is a 19mm hex. Screw nut back on with the ratchet until tight. Close the cover. Move back to the trunk and reconnect the negative battery terminal.

At this point, you can crank the car up to make sure everything is working properly. Be sure to clear any tools from the engine bay and that nothing is in the way of moving parts.

Step 30: After everything clears and the engine sounds good, replace the engine cover. Before sliding it back on, remove the PVC vent tube and oil fill cap first. Be sure to slide it under the positive power cable and black PVC cable. Use the 10mm deep well socket to tighten down the 6 chrome cap nuts. Tighten until snug. I believe the torque setting for the engine cover caps is 7 ft-lbs if you want to torque them.

Step 31: Replace the microfilter housing to its location and screw the 4 T30 screws back in place. The housing simply slides in at an angle first and seats itself. Replace the microfilter and its cover. Be sure to twist the 3 retaining clips down tight.

Installation of the remaining parts is reverse of removal. If you cant remember, go back through the steps and replace everything back into its location. Clean engine cover if you have a chance and replace tools back to their locations. Dispose of the old ignition coils and spark plugs properly. Thanks for reading.

There are several codes for faulty igntion coils and spark plugs. Be sure to have the codes read and do research before having to replace them.
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Old 03-26-2014, 05:10 PM   #3
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Although this thread is old I imagine it's a great resource for those of us doing some maintenance this summer. Just wanted to make one adjustment - if you do opt for the iridium plugs as listed above DO NOT set the gap or even check the gap. Gapping the iridium head with a standard gap tool will microscopically break the iridium contact point and cause subtle misfires - this will ruin the plugs.

Thank you for the DIY, very detailed!
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Old 03-26-2014, 07:15 PM   #4
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Didnt know that thank you. so its already gapped perfect?
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Old 03-27-2014, 06:48 PM   #5
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From what I've been told, yes. I made the mistake of checking the gap on iridiums I installed in our MDX and had a series of misfires. After much delay and diagnosing I was told checking iridiums was a cardinal rule.
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Old 09-01-2014, 02:08 PM   #6
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Thanks for the detailed description. As a first time DIY project on the car I was a little nervous. Unfortunately I did not see the ending of the thread about not gapping iridium plugs. I did and when I started the car all was good. But took it out today and misfiring like crazy. Any suggestions? Or just start over and replace the plugs. Thanks.
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