N55 Spark Plugs and Coils

Spark plugs are a scheduled job on the N55. Ignition coils aren't: BMW gives them no interval, so you replace the ones that fail. The coils come out to reach the plugs anyway, so here is how to tell what your car needs and which plug it takes.

Covers these US N55 cars: 135i and 335i (E82, E88, E90, E92, E93, built from March 2010), 335i (F30, F34), 435i (F32, F33, F36), M235i (F22, F23), M2 (F87), 535i (F10, F07), 640i (F06, F12, F13), 740i and 740Li (F01, F02, built from July 2012), X3 and X4 (F25, F26), X5 and X6 35i (E70 and E71 built from April 2010, F15, F16). Not the ActiveHybrids.

Plug or coil?

Misfire codes stored in the engine computer. Note which cylinder each one points at.
Rough idle. A parts vendor points out that a failing coil looks just like worn plugs from the driver's seat. Test first, then buy.

IA EURO illustration of one failed coil from our bench with the boot end circled — Figure 1A failed coil, with the rubber boot end circled: the end that goes down into the plug well. From our bench.

Figure 1A failed coil, with the rubber boot end circled: the end that goes down into the plug well. From our bench.

The coil swap test

Shop rule of thumb, not BMW's (a parts vendor teaches it too): with the ignition off, swap the suspect coil with the coil on another cylinder. Clear the fault, drive, and read the faults again. If the misfire moved with the coil, it's the coil. If it stayed on the same cylinder, look at that plug. Still there after new plugs and a clean swap? Then it isn't a coil or a plug: see the fuel injector guide.

Which plug your car takes

Most N55 carsBMW 12 12 0 037 582Bosch, six per car. Every car on this page except the two below.

Plug $18.99 →Coils and plugs $366.99 →

M2 (F87) and X4 M40i (F26)BMW 12 12 0 039 634A different plug, and a shorter service interval. On the X4 it's the M40i, built December 2015 to March 2018. The X4 xDrive35i takes the standard plug. Not sure? Send us your VIN.

NGK plug $24.99 →Coils and plugs $397.99 →

Ignition coilBMW 12 13 8 616 153Delphi, six per car. One coil number for every car on this page, M2 included. Each kit above is six coils and six plugs.Coil $42.99 →

How often

Plugs: what BMW givesIts US service chart puts the plugs at about 60,000 miles on the F-series cars, about 30,000 on the M2 and the X4 M40i. For the E-series cars here we found no US figure, so go by the car's own reminder if it shows a plug item.

Plugs: shop rule of thumb, not BMW'sOwners and parts vendors run 40,000 to 60,000 miles on a stock car and 15,000 to 35,000 on a tuned one.

CoilsBMW gives no interval. Its coil job starts by reading the stored faults, so coils go when they fail. Owners and vendors often do them with the plugs: 60,000 to 70,000 miles stock, 30,000 to 40,000 tuned.

How long: a parts vendor's N55 walkthrough says about 2 hours, not a BMW figure.

Do the coils too?

Replace a coil when the swap test points at it, when its boot is torn, or when it's been soaked in fuel: BMW says fuel on the silicone can make a coil fail. The rest can stay. Shop rule of thumb, not BMW's: if they're past the owner range above, or the car is tuned, do all six while they're out. Only parts cost extra. Doing the valve cover? Owners pull the coils for that too, so do the plugs then.

Rust on a coil sleeve or a plug shell? Shop tip from our bench, not BMW's: we pulled a rusty set at 185,000 miles from a car that had sat abandoned. Our guess is the coil's top seal let water into the plug wells. If you see rust, change the coils and plugs and check the wells for water.

IA EURO illustration of a coil from our bench with rust on the metal sleeve — Figure 2Rust on the metal sleeve of a coil pulled at 185,000 miles. From our bench.

Figure 2Rust on the metal sleeve of a coil pulled at 185,000 miles. From our bench.

What you need

Thin-wall plug socketA parts vendor's N55 walkthrough uses a 14 mm, 12-point thin-wall plug socket, 3/8 extensions and a hook pick, and says the narrow plug well won't take a normal chrome socket. BMW's own tools are plug spanner 12 1 220 and plug installer 12 1 230.

Flexible extensionBMW wants one with a bend of at least 8°. Rigid tools risk breaking the plug insulator. No locking variable connector either.

AlsoTorque wrench, compressed air, goggles, six new plugs.

Ignition off, goggles on, for the compressed air.

Never oil or grease a coil boot. It's talc-coated. Never let a plug fall into the well either: BMW says it can close the plug's gap and make the idle rough.

Out in this order

Engine coverOff first, if your car has one.
Coil coverWhat comes off first varies: rear coil cover, bulkhead sound insulation, clean-air pipe, or coil cover and cable channel.
Bracket and clipOxygen sensor connector bracket, then the cable clip.
CoilsUnplug each one, then pull straight up, slowly.
Plug wellsBlow clean before any plug is loosened.
PlugsFlexible extension only.new plugs

Torque and gap

Spark plugs (a parts vendor's figure)23 Nm (17 lb-ft)

Coil cover screws, M6 x 304 Nm

Coil ground cable screw5 Nm

Oxygen sensor connector bracket8 Nm

Cable channel screws5 Nm in BMW's current table, 8 Nm in an older one: send us your VIN for yours

BMW's repair data has no N55 plug torque, so 23 Nm is the vendor's number, not BMW's. BMW's steps say to use the torque on the plug's packaging if the box gives one. Coils have no bolt: they push on and stay put on their rubber cap and an anti-twist notch. Gap: we found no BMW or Bosch figure for the stock plug, so we print none.

Out

Read the faults and note them. Ignition off.
Covers off. Use the map: BMW doesn't say which set your car has, so look before you pull.
Figure 3The cable channel over the coils, held by screws at each end. Generic layout: yours may differ.
Figure 3Close
Free the oxygen sensor connector bracket and the cable clip.
Unlock and unplug each coil connector without crushing the wires.
Figure 4A coil connector: swing the latch over (curved arrow), then pull the connector off (straight arrow). Generic layout: yours may differ.
Figure 4Close
Coils out in one smooth pull, straight up, slowly. The silicone boot can tear. Lay them out in cylinder order.
Blow every plug well clean, goggles on, before any plug is loosened. Dirt left behind can drop into the cylinder or loosen the plug.
Plugs out with the plug spanner on a flexible angled extension. Look at each plug seat once the plug is out.
Figure 5An old plug coming out in its thin-wall socket, carbon on the tip. From our bench.
Figure 5Close
Figure 6Coils and plugs out, laid in a row so each pair stays with its cylinder. From our bench.
Figure 6Close

In

Start each new plug by hand on the installer tool and run it in to the stop.
Figure 7Starting a new plug by hand on a long installer tool. Generic layout: yours may differ.
Figure 7Close
Nothing on the thread. BMW says no grease, graphite or copper paste. A vendor adds no anti-seize on these plated plugs.
Torque it with the torque wrench on the plug spanner (see above).
Figure 8A thin-wall plug socket on a swivel joint and extension: the flexible setup BMW asks for. Generic layout: yours may differ.
Figure 8Close
Coils in, pushed to the stop, with a slight twist if needed. Check the anti-twist lock. The rubber cap has to wrap the whole sealing collar on the head cover.
Figure 9End-on view of a coil's rubber boot. When it goes back in, the rubber cap has to wrap the whole sealing collar. From our bench.
Figure 9Close
Plug in and close each connector latch without force. BMW says a bent latch won't lock any more.
Bracket, clip and covers back on at the torques above.
Clear the faults, start it and check the idle.

Reset the spark plug reminder

Last, and only if your car shows a plug item. BMW's in-car steps, written for the speedometer display: ignition on, engine off. Hold the trip reset button about 10 seconds until the first service item shows. Step to the plug item with a short press of the stalk button. Hold about 3 seconds until Reset? shows, then about 3 seconds again to confirm. Owners (not BMW) say F-series buttons differ.

The 80 percent rule. In the car, BMW only lets you reset an item once it is under 80 percent available, with no Check Control message and the date right. Above that you get a reset lock, and only a shop's BMW diagnosis tool clears it. Our reading, not BMW's: change plugs very early and you can hit this.

Where people mess it up

Wrong plug. The M2 and X4 M40i take 12 12 0 039 634. Everything else takes 12 12 0 037 582.
Skipping the blow-out. Dirt can drop into the cylinder.
A rigid extension. BMW says it risks breaking the plug insulator.
Dropping a plug down the well. It can close the gap and make the idle rough.
Anything on the thread. BMW says grease, graphite and copper paste can harm the plug body and its threads.
Yanking coils and forcing connectors. A vendor warns the connectors are brittle and the inlet pipe can crack.
Resetting before the work is done. BMW says reset after.

More N55 basics: engine air filter and cabin filter.

Steps, torque values and part rules come from BMW's repair instructions for the spark plugs and ignition coils and BMW's US service chart, with owner and parts vendor notes labeled where we use them. Part numbers come from BMW's parts catalog up to 2020. Check yours by VIN.