PARTS
NGK Spark Plug: 94201 (OE# :12120040551)

TOOLS REQUIRED
-Spark plug socket buy here
-Torque wrench buy here
-E TORX sockets buy here
-Spark plug gap gauge buy here
-10mm socket buy here

TIME
1.5 hours

Spark plugs are a part of your car’s regular maintenance, and changing them on time will ensure smooth engine operation and good fuel economy. On the B58, it’s recommended to change the spark plugs every 50,000 miles for cars that are stock, or 20,000-30,000 for cars that are tuned or modified.

Fortunately, changing the spark plugs on your B58 powered BMW is not difficult or expensive. In fact, you’ll spend more time getting to them than actually changing them.

While the ignition coils don’t have a set maintenance interval, you may want to change them as preventative maintenance if your car has high mileage. My personal recommendation is to change the coils at 70k miles based on my experience with my E90. Since you have to take the ignition coils out to get to the plugs anyway, it makes sense to change them all at once.

INSTALLATION

Step 1
Loosen the 10mm nut to remove the negative battery cable from the terminal.

Step 2
Lift straight up on the acoustic engine cover to remove it.

Step 3
Remove these triangular covers on both sides.

Step 4
Remove four E18 bolts to remove this chassis brace. You may need some extra leverage.

Step 5
Carefully pull the wire out of this rubber insulation and remove the insulation from the car.

Step 6
Remove the seven 10mm screws to remove this plastic cover.

Step 7
Carefully remove this foam sound deadening so it doesn’t rip on it’s way out.

Step 8
With everything out of the way, you now have unobscured access to all six spark plugs.

For the spark plugs I went with the NGK 94201 which is an OE plug for the 340i. BMW has also used Champion plugs in the B58. My original plugs happened to be NGK but don’t be surprised if you see a different brand when you pull you original plugs.

The NGK 94201 is made specifically for the B58 and is pre-gapped to .030. You can use a gauge to double check that the gap is correct on all six spark plugs, although, they are packaged nicely with a cardboard tube that protects electrode.

There is a lot of discussion online whether or not you should change the gap so something like .022. For cars that are stock or stock with a basic stage 1 tune, the stock gap is fine and you can use the 94201 plugs straight out of the box. If you are running other mods like a big turbo or ethanol, check with your tuner and see what gap they recommend for your car.

Step 9
Unlock the ignition coil harness by lifting up on the center tab while simultaneously pulling out on the grey tab.

Step 10
Loosen the E8 bolt on top of the coil. Note that it’s part of the ignition coil and won’t come all the way out.

Step 11
Remove the spark plug. The B58 plugs use a thin wall, 14mm, 12 point socket. This Kies Socket is magnetic which makes changing the plugs a breeze.

Step 12
Carefully hand thread the new plugs to avoid cross-threading. DO NOT USE ANY KIND OF LUBRICATION ON THE THREADS.

Step 13
Torque the new spark plugs to 23NM.

Step 15
Re-install the ignition coil and plug in the harness. The tightening spec on the E8 bolt is 8NM.

Follow these steps for all six spark plugs. Before re-assembling everything, open the garage and start the car to ensure there are no misfires.

INSTALLATION VIDEO

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