BMW B58 Spark Plug & Ignition Coil Maintenance Guide
Maintaining the spark plugs in your BMW B58 engine is essential for ensuring smooth power delivery, maximizing fuel economy, and preventing misfires. While BMW officially recommends 60,000 mile intervals for spark plugs, you may need to tighten that interval if your car is tuned, and/ or you drive aggressively.
Fortunately, changing spark plugs on a B58-powered vehicle is a straightforward and cost-effective DIY. While the process itself is simple, the majority of the labor involves removing the engine plastics and acoustic foam to access the rear cylinders. Once you have clear access, the actual replacement is quick.
Pro tip: While there is no official service interval for the ignition coils, they typically last 80,000 to 100,00 miles. If you are replacing your spark plugs in that range, you may want to replace the coils too as preventative maintenance to avoid a failure on the road. Ignition coil part number BMW - 12138643360.
Overview & Cost
Difficulty: Easy - intermediate
Time Required: 1.5 hours
Estimated Cost: $120
Fitment: BMW 240i, 340i, 440i, 540i (or any BMW with B58 engine)
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
Parts
Spark plugs: NGK 94201 (BMW - 12120040551)
Ignition coils (optional): BMW - 12138643360
Note: Spark plugs and coils are sold individually. You will need 6 for the B58, or 4 for the B48.
Spark Plug Replacement DIY
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.
NGK 94201
For the spark plugs I went with the NGK 94201 which is an OE plug for the F30 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 your 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, and that the idle is smooth.
Compatible models
BMW M240i (2017-2021)
BMW M240i xDrive (2017-2021)
BMW 340i (2016-2018)
BMW 340i xDrive (2016-2018)
BMW 440i (2017-2020)
BMW 440i xDrive (2017-2020)
BMW 540i (2017-2019)
BMW 540i xDrive (2017-2019)
BMW 740i (2017-2019)
BMW 740i xDrive (2017-2019)
Watch the DIY video
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