Why The BMW 335i And Other Cars With The N54 Engine Are Ticking Time Bombs

335i Topshot 2

The original BMW 335i is a bit of a marvel. At the time of its release, everyone thought BMW had gone mad. Why sacrifice the character of a naturally-aspirated engine when the German marque could’ve just built a modern version of its M30 big-six? Well, it wasn’t long until drivers noticed smooth, almost lag-free power delivery and tuners realized they could add the better part of 100 horsepower with a few bolt-ons and a tune. How’s that for a bit of humble pie? However, as these cars depreciated, it became apparent that they were quite expensive to keep going, and over the past few years, the costs have grown much higher.

Really, it’s not just the 335i I’m talking about – it’s anything with the N54 twin-turbocharged inline-six engine. Certain years of 135i, 135is, Z4 sDrive35i, Z4 sDrive35is, 335is, 535i, X6 xDrive35i – all that stuff. The N54 is a neat engine, but almost everything bolted to it is terrible. The turbochargers develop wastegate rattles that require serious hours to repair, the plastic valve cover cracks, the charge pipes leak, and the high-pressure fuel pump can go bang. However, most of these pale in comparison to the issue of fuel injectors.

335i Engine Bay
Photo credit: BMW

The N54 uses piezoelectric direct fuel injectors, and because it’s a fairly early application of this tech on a gasoline engine, they tend to go a bit wrong. BMW had to revise injector design 11 times during the engine’s production, eventually landing on the latest Index 12 injectors. However, Index 12 injectors can still fail, and you’re not ready to hear what each replacement injector costs.

Fcp Euro N54 Injector
Screenshot: FCP Euro

Take a deep breath. From reputable online retailer FCP Euro, Index 12 injectors for the N54 inline-six cost $549.99 each. Yes, each. What’s more, it’s not recommended to mix Index 12 injectors with Index 1-10 injectors as a calibration change occurred for Index 11, which means that it’s recommended to replace injectors bank-by-bank. Considering an N54 has two banks of three cylinders, this means a minimum outlay of $1,649.97. If you want the peace of mind of replacing all six in one go, that’s $3,299.94 worth of fuel injectors. That’s enough to mechanically total a high-mileage E90 335xi.

N54 Injector Diagram
Screenshot: BMW

Index 12 injectors weren’t always this expensive, so what the hell happened? In short, there was a parts structure change. The updated fuel injectors for the N54 engine carried a part number of 13538648937 and were made unavailable outside of recall or warranty work in 2018. However, they were basically identical to the then-recently updated direct injectors found on the S63 V8, part number 13538616097. Both part numbers have since been combined under part number 13538616079, still identical to the injectors on the S63, albeit much more expensive than before.

So are there any aftermarket alternatives to these pricey VDO-manufactured injectors? Yes and no. There are companies out there that promise to rebuild these fuel injectors. However, rebuild quality varies wildly, so it’s a roll of the dice on whether you’ll need to just buy brand new injectors anyway. I’d also advise against ordering cheaper injectors from eBay as many are counterfeit with improper calibration values printed on the parts. As replacing N54 injectors requires registering the new injectors in the engine control module, punching in correct injector calibration values is critical to avoid misfires.

335i 2
Photo credit: BMW

As it sits, there is no cheap way to properly replace N54 fuel injectors according to servicing guidelines. It’s a painful reminder that once-bleeding-edge technology will always be expensive to keep going as few first shots are ever perfect. If you’re in the market for an N54-powered BMW, it’s a good idea to ask for service records and see if the injectors have ever been replaced. If all six are now Index 12 injectors, you’re likely in the clear. If not, be sure to keep a few grand lying around for when the inevitable happens. Really, that’s good German car advice in general.

Lead photo credit: BMW

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80 Responses

  1. Man, I don’t miss my 335i one bit. Every expensive thing on that car that could go wrong did:

    1) Multiple injector banks replaced
    2) Multiple high pressure fuelpumps
    3) Wastegate
    4) Plastic oil pan cracked, leaked and stranded me
    5) Multiple airbag occupancy mats (had to leave the belt clicked)
    6) Water pump failed and shot water all over the alternator, taking it and the electrical system with it

    I finally donated its carcass to a radio station. It was six years old. By then all the plastics on the inside were turning to goo. What a mess of a car.

  2. It’s crazy these jumped in price so much. I replaced all six injectors in 2017 with index 12s and it cost me roughly $130/ea. That seemed like a lot then. This is bonkers. The N54 and the 335i, in general, definitely has some issues, but they’re mostly manageable. Every time I think about selling mine, I take it out for a drive and I’m like Pacino in Godfather III.

  3. Injector’s aside, a friend of mine built a 335i as a fairly serious track car, spending tens of thousands of dollars on performance and durability upgrades (likely approaching six figures). I can tell you from direct eyewitness testimony that these cars do not hold up well to road course track duty. Constant limp mode issues, failing turbos, problematic fuel systems, and much more. He also blew TWO N54 engines in the process. One was a spun #6 rod bearing, and the other was a grenaded piston.

  4. On the one hand, some automakers like to load up their cars with cutting-edge technology that isn’t fully baked yet, with predictable results.

    On the other hand, sometimes they forget how to bolt on the wheels in such a way that they don’t just fall off right after the car gets on the road.

    Whaddaya gonna do?

  5. And for the record, there are no replacement injectors listed on rockauto either.

    You can get turbos for as little as US$359, valve covers can be had for as little as US$135 and the HPFP can be had for *only* US$1400. The other stuff is also unavailable.

    On the bright side. the wastegate rattle thing looks like a no-cost DIY fix… I saw a youtube video on it

    But aside from that, this article reaffirms why I avoid Euro luxury cars and how “German Quality” is a joke… particularly when it comes to BMWs and VAG products.

    1. Many years ago I waited months for a door lock barrel to be delivered for a VW I owned. It had to be calibrated to the door lock system, so it was not an easy DIY repair. After months of waiting, and going in to the dealer to check (It was on my way home, so why call) the parts manager said he “would never by a VAG product.” I took the hint. Anyway, no worries for this Lexus fanboi, and parts are much less expensive. Muuuuuch less.

      1. There are 4 wastefate rattle fixes
        1) Some tunes have a wastefate rattle reduction mode which is not 100% effective…usually isn’t.. but is worth the try…if it just started, may hit the spot
        2) There is an adjustment on the wastgate you can make to reduce or remove the rattle, but is not 100% effective depending on how bad it is..
        3) Replace the garbage Mitsubishi turbos for anything but…Pure is one of the best replacements with known reliability
        4) Delete them and put 328i badges on it

  6. It’s lame that a 3 series has problems like this. I’d expect these kinds of problems on a 7 series which is very very expensive when new, and is expected to have the very newest tech. I’ve considered getting a used BMW coupe, but when I read about things like this I have doubts.

  7. We have a 2010 1 series with the N54.

    “ticking time bomb”? Sure, only if you decide that routine maintenance is optional. But this would apply to any car then, wouldn’t it?

    The fuel injectors got replaced, as per the schedule, at 100k miles. This was in 2018. We used an indie BMW specialty shop, who used a quality aftermarket part.

    But assuming I was the kind of person who can’t RTFM regarding scheduled repair or replacement is parts, you think $3300 is enough to total a car? Seriously?

    The math is this: $3300 on a scheduled repair on a fully paid off garage kept car that runs really well and could run well for several more years vs spend cash or take on a monthly payment on a CPO or new car for several years, which costs WAY more than $3300 in the long run, and would likely increase my insurance costs.

    Also, many of the problems you describe occur if you drive the car hard all the time, and then forget to follow a more frequent maintenance schedule befitting that kind of usage. If you use it as a DD, the only thing I recommend beyound routine things is replacing all the coolant hoses to the braided stainless steel, and every 75k replace the water and fuel pumps. But….I would do that for any car.

    1. Thanks for the reminder to hug my 128, and plant a kiss on its non-turbo N52 straight six. Every time it goes in to my independent BMW shop they remind me to call them first if I ever sell.

  8. I see this rant is limited to the N54. The N55s solve many of these issues with slightly better numbers (torque curve peaks a few hundred revs sooner). As far as injectors, you can swap out individually and mismatch generations and engine management won’t bat an eye. I have two N55s (one high and one low mileage) and have swapped a single injector between the two by hand picked up same day from Autozone for $65. A major drawback is you can’t boost pressure to the moon without some additional peripheral changes.

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