N54 FAQ (With actually useful information)


Oct 18, 2016
2009 E93 335i
In an effort to consolidate and reduce the number of sticky threads as well as create a collective point of reference for frequently discussed topics, this thread is being made. Feel free to post suggested threads and topics and I will attempt to cover them here.



Plugs, Injectors and Coils:

Brake Pads and Rotors:




BOV Spring Sizing:

Motor Mounts:

xHP Flashtool:

Secret / Alternate Part Numbers:


Bushings and Mounts:

Upgrade Path:

LPFP Fuel Line Upgrade:

Injector Coding and Setup:


Oct 18, 2016
2009 E93 335i
Credits to who compiled this list of common problems:

E82/E90/E92/E93/E60 135i/335i/535i
Spark Plugs Need to be done every ~50k Miles. More often if tuned.
Oil Leaks:
Valve Cover Gasket and Oil filter Housing gasket(s) will start to leak around 100k miles
Oil pan gasket leaks begin to show up frequently north of 120k
Rear Main Seal leaks are uncommon but do happen
Turbo feed/drain lines occasionally leak
Coils will begin to fail around 80-100k miles, best to replace all 6 at once.
Automatic Transmission: Cars will need to be serviced with new pan and fluid as well as Mechatronics seal and sleeve before 100k miles.
Main Drive belt and tensioner should be done before 100k. Main drive belt can/will be eaten by crank pulley if failed and make its way behind front main seal into timing chain and oil pickup possibly causing catastrophic engine destruction
Beware of <2008 cars having power steering pulley sub frame contact issues
If Oil filter housing gasket has leaked on belt this must be done sooner
Factory Charge Pipe (Plastic) Can explode at even stock boost levels. If tuned/running higher than factory boost level, upgrade to metal.
For the most part all cars have had a few HPFP’s done by now and this doesn’t seem to be an issue any more but if you are getting long cold starts and pressure drops in logs, its something to investigate
Injectors sometimes fail. They have been updated a number of times and are currently on a -12 revision. Most cars shipped with -05 to -07 injectors. Decouplers should be replaced at the same time. Injectors need to be coded to the car.
Depending on driving aggressiveness Thrust arm bushings will fail around 100k. Can be replaced with ball joint type aftermarket ones.
Walnut Blasting necessary as often as every 40-50k miles. Do this with new intake manifold gaskets
MSD80 (2006-early 2008 cars) have very rare ECU Injector MOSFET driver failure. Drivers require replacement and can be serviced. New ECU not necessary
Waste gates: Waste gate rattle both internal and external to the turbo will begin in some cases as early as 70k depending on a number of factors. Some things can directly cause this however like vacuum lines. Adding catless downpipes will magnify waste gate rattle issues. Failing wastegate thrust bearings can cause under/overboost conditions as the wastegate arms inside the turbo can Jam.
Vacuum lines going from the vacuum pump to the vac canisters and ones going from the waste gate solenoids to the turbos can crumble and leak. Will cause underboost codes and or waste gate rattle in most instances.
Smoking: Caused by a number of different things from the PCV system to turbos. The valve cover PCV system can internally fail and cause significant smoking/consumption. Adding downpipes to the car further makes the smoking more apparent as the cats are no longer ‘filtering’ the smoke coming through them.
Tunes/Tuning: The N54 is run by an extremely complicated ECU (MSD80/MSD81) and when you begin to tamper with this many things can happen
After adding a tune, if you haven’t already, you will have to do plugs/coils soon as the increase in boost level taxes the coils further
Piggybacks (Jb4) are typically the best bang for your buck as far as user interface and customizing your specific setup.
Piggybacks can ‘annoy’ the factory automatic Trans (or DCT) computer because of the underrated load values being sent to the TCU. This can sometimes cause slipping/Jerky Shifts. A proper ecu flash to go with the piggyback can remedy this if affected.
MHD Tuning is a popular ECU flashing method with an android tablet
There are a number of ‘pro-tuners’ around that can do a decent job of utilizing what tables they do have to work with to get the most out of your car.
Fuel System: When ‘tuning’ to extremely high power levels, fueling needs become a concern. People are currently adding secondary in tank pumps, secondary high pressure pumps and secondary direct port injection fuel rails as well as meth to compensate.
Cooling System:
Water Pump/Thermostat is good to around 100k. Past that and you’re on borrowed time.
Oil cooler: If you don’t have a factory installed one, you need one as any spirited driving will drop you into limp mode. If you do have one, this alone won’t keep you safe if you do an extensive amount of hard driving/track/drift/etc. Additional aftermarket oil cooler setups are recommended
Adding an intercooler is a good idea for any car street or track to keep the extremely high IATs down that are caused by the twin turbos.
Vanos: Expect to do vanos solenoids around 100k or sooner depending on how often the oil was changed. You can sometimes get away with cleaning them but typically vanos codes (2A87/2A88) will return. Worst case scenario is oil pressure to vanos hubs is being lost through cam trays (“hook ring seals”) Cam trays/ledges will need to be replaced as well as the updated Teflon cam seals
Differentials: If you’re into performance driving you will want an LSD. The factory open diff is sufficient for many but not most. There are a number of aftermarket alternatives available in this regard from gear type to clutch type.
“Limp Mode”: Arguably the most infuriating thing about these cars is they will frequently for a number of reasons engage limp or failsafe mode (half engine light). This can be caused by a number of things from a cooling system issue, under/over boost, vanos, fuel injection, misfire, etc.
Boost Leaks: Factory Charge pipes going to the throttle body randomly fail at stock or elevated boost levels. The factory diverter valves can also leak. The Hot side charge piping rarely leaks. Adding an intercooler also adds more couplers and clamps that can leak. Boost leaks can and will cause extra wear on the turbos as the ECU attempts to compensate for the loss of boost by working the turbos harder.
Oil System: Besides the aforementioned leaking issues, these engines are sometimes riddled with sludging issues because of BMW’s suggested oil change intervals. This can sometimes lead to stuff like Rod knock although this is fairly uncommon and seemingly random
Battery: Extremely overlooked and neglected this simple thing can cause widespread havoc on your car. Keep it in good condition. When it’s starting to fail the IBS system will decouple the battery after you shut the car off thus turning the water pump off after the car shuts down that acts as a ‘turbo timer’ to cool the turbos down after shutdown. New Battery’s need to be ‘registered.’ If changing battery capacity, battery needs to be ‘coded’ to CAS module.
DMTL pumps randomly fail. Emissions readiness monitors are sometimes extremely annoying to get to set.