BMW N53 Engine ProblemsPin

The 5 Most Common BMW N53 Engine Problems

The BMW N53 engine was produced from 2006-2013. Being the final naturally aspirated inline-6 that BMW will likely ever produce, it is the last of a tradition from BMW that dates back to 1968. As a result of BMW’s constant improvements to their straight-6 formula, the N53 is a fantastic and well-rounded engine, completely with many of BMW’s most modern engine technology including direct injection and double-VANOS.

However, that doesn’t exclude the N53 from having a number of common issues, primarily consisting of high pressure fuel pump failure, injector failure, NOx sensor/catalytic converter wear and tear, spark plug failure, and coil pack failure. In this guide, we’ll cover those 5 BMW N53 common problems in detail.

BMW N53 Background

For all intents and purposes, the N53 engine can be thought of as an extension of the N52 inline-6 that was produced from 2004 to 2015. The two engines are almost identical in terms of their overall construction, barring a few changes. The primary difference is that the N53 was designed to be a high-efficiency version, leading to changes in the design of the N53’s fuel and exhaust systems. BMW was able to reduce fuel consumption in the N53 engine by adding direct injection and a nitrogen oxide storage catalytic converter. This catalytic converter required low sulfur content fuel to run properly. 


Fitted in BMW E9x 3-Series, E60 5-Series, and even the F10 5-Series until 2011. The N53 replaced the N52 in most markets, except for the North American Market and Australia.  These markets were excluded due to high sulfur content in the fuel. While most markets got the updated BMW N53, the U.S., Canada, and Australia continued to get the N52.

5 Common Problems with the N53 Engine

Like its N52 predecessor, the N53 truly represented BMW at their best as far as the inline-6 engine layout is concerned. Over 45 years of developing inline-6 engines led BMW to truly nail down how to build an inline-6 that was not only powerful but also extremely reliable. That all culminated in the N53.

Ultimately, the N53 is an extremely reliable engine that only suffers from a handful of notable engine problems. While the engine has had issues with direct injection fuel pump failure (similar to most early BMW direct injection engines), injector failure (see previous parenthetical), NOX issues, spark plug failure, and coil pack failure, there are very few true N53 engine problems to note. Here are the N53 engine problems that we’ll be covering here:

  1. Fuel Pump
  2. Injectors
  3. NOX Sensor/Cat Issues
  4. Spark Plugs
  5. Coil Packs

If you would rather consume this content via a video, check out our BMW N53 Common Problems video below:

1) N53 High Pressure Fuel Pump (HPFP)

This is the first common and most prevalent issue to come up with the N53.  High Pressure fuel pumps were such an issue when the engine first came out that BMW issued a recall on the engine. The N53 uses the same HPFP as the BMW N54, and these issues are well documented. The high pressure fuel pump is a very important element of any direct-injected engine’s operation, as it is responsible for pressurizing the fuel before it reaches the injectors and is sprayed into the combustion chamber.

There are a few reasons why high pressure fuel pump is such a big headache on the N53. For one, a failing high pressure fuel pump can lead to all kinds of drivability issues. Additionally, BMW high pressure fuel pumps are notoriously expensive and difficult to replace. With it being such a common issue, there are tons of forum posts about N53 HPFP failure occurring randomly and without any consistency as to when the failures occur. Some N53 owners experience a failure as early as 15,000-20,000 miles while others make it north of 100,000 miles without issue.

If you are interested in reading about high pressure fuel pump failure in more detail, take a look at our BMW N54 High Pressure Fuel Pump Failure article.

Symptoms of N53 HPFP Failure

  • Long crank
  • 1/2 engine light
  • Rough idle
  • Stuttering acceleration

When the high pressure fuel pump is failing it will not deliver enough fuel to the engine for proper operation. The lack of fuel flow is what causes long cranks, rough idling, and stuttering while accelerating.  The 1/2 engine light may illuminate and the car will likely continue to drive until the HPFP completely fails and does not flow adequate fuel for the engine to fire.

Mileage for Failure

High pressure fuel pumps on the BMW N53 may fail at any mileage; many likely failed early on and were replaced under the recalls and extended warranty.  In 2012/2013, after multiple attempts, BMW finally re-designed the HPFP which seems to have resolved the issues. If you are looking into purchasing a model with the N53, be sure to check the maintenance records to ensure the HPFP has been replaced either by recall or by the previous owner.  Most N53 HPFP’s likely experienced failure early on and received the updated fuel pump, but there may be a few out there still running the original faulty part.

2) N53 Fuel Injector Failure

The N53 went from port injection to direct injection with Piezo injectors (similar to the BMW N54).  With this change, came a learning curve and lots of changes and reprogramming to these parts.  Though the BMW N53 and N54 both used direct injection featuring Piezo injectors, the actual part number and injectors are different on each engine. Despite this difference, they suffered a similar fate with common failures.

Symptoms of N53 Fuel Injector Failure:

  1. Misfires
  2. Limp Mode
  3. Rough Idle
  4. Poor Fuel Economy
  5. Check Engine Light

Unlike the HPFP issue that does not flow enough fuel, the injectors typically fail by developing leaks and dumping extra fuel into the cylinders.  This extra fuel causes misfires, rough idle, poor fuel economy and potentially check engine lights and limp mode.

If you do need to replace the injectors, do not buy them refurbished or used, and try to get them to match the same index.  The newer fuel injectors that fixed the early issues have different indexes; it is important to note that different index fuel injectors can not be mixed on the same bank (i.e. cylinders 1-3 or 4-6).  After replacement, they will need to be coded.  Not replacing them properly can cause the engine to still run rough, which may lead into the next two issues.  These 3 of the 4 common N53 problems have to do with misfires and rough idles.

3) Bad BMW N53 NOx Sensor/Cat

NOx sensor, NOx cat issues are some of the most frequently reported issues on the N53 engine, especially as the engines age and exhaust components begin to fail. Since the N53 was designed to be a low-emissions engine, it is equipped with both a NOx sensor between the last CAT and rear back box and a NOx catalytic converter.

A NOx sensor has a pretty straightforward job; it measures the amount of nitrous oxide that is emitted by the engine at two points in the exhaust system. A NOx catalytic converter is used to collect the excess NOx produced by the N53. The N53 produces more NOx than a typical engine due to the fact that it is a stratified charge engine, allowing for it to run a higher compression ratio, increasing efficiency but also raising NOx production.

Over time, the NOx sensor can begin to malfunction, and the NOx catalytic converter fails to capture an adequate number of NOx ions, leading to performance issues and other engine problems. High sulfur content in fuel leads to faster degradation of NOx cats, which is why the N53 was only offered in parts of the world where fuel has very low sulfur content.

Symptoms of Bad N53 NOx Sensor/Cat

When either the NOx sensor or NOx cat begins to malfunction, there are a number of noticeable symptoms that generally accompany that. In the majority of cases, neither of these issues are truly serious and you’ll be able to drive your car regardless. However, a failed NOx cat can cause you to fail MOT or emissions testing if not repaired first.

  • Rough Idle
  • Metalic rattling sound on startup
  • Smoke coming from the exhaust until engine is warm
  • “Aging NOx Catalytic Converter” engine code
  • Inconsistent engine performance

Bad N53 NOx Sensor/Cat Diagnosis/Fix

Due to the fact that many of the symptoms of a bad NOx sensor/NOx cat fall in line with a number of other common N53 failures, including bad injectors and a bad HPFP, it is important to make sure that the sensor/cat is truly the issue and not something else. NOx cats are notoriously expensive to replace, so it is a good idea to do a thorough diagnosis before purchasing a new one.

Luckily, diagnosing a failing N53 NOx sensor/NOx cat is relatively easy with a diagnostic tool. BMW INPA is the most commonly used diagnostic tool to check for NOx issues, as it will tell you which engine mode your N53 is running at any time. If you can see that your engine is entering the stratified engine mode, you likely don’t have an issue with either component. If the engine fails to run consistently in stratified mode, there is an issue with either the sensor or the cat. If the diagnostic tool is presenting an “Aging NOx Catalytic Converter” code, it means that the cat is to blame for your issues.

Ultimately, there are a few solutions if your NOx catalytic converter is going bad. You can replace the aging unit with a fresh one, which can be extremely expensive but will guarantee that you won’t have any issues smog testing. There are also a number of NOx cat delete options on the market via software tuning. A company called Bimmerproffs offers a NOXEM emulation tune for about £320 which tricks the DME into thinking that the cat is in working order. You can also install an aftermarket high flow cat and have Bimmerfroffs tune your DME to accommodate that. You can check out their website here.

4) N53 Spark Plug Failure

Not a huge issue on the BMW N53, but something I saw come up several times with owners attempting to correct their misfire and rough idle situation. Obviously, spark plugs are a common maintenance item regardless, but N53 plugs have been known to wear prematurely, causing misfires and rough idles. Leaking fuel injectors dump extra fuel near the spark plug tips causing premature wear.  Also, if you have had a valve cover gasket leak, there is a chance that oil has soaked the plugs.

Symptoms of Bad N53 Spark Plugs

  • Rough idle
  • Stuttering acceleration
  • Loss of power & torque
  • Reduced engine responsiveness

In addition to premature wear, spark plugs naturally wear down over time and become less effective or faulty, causing the same symptoms above. They should be replaced roughly every 40,000-50,000 miles, and are a cheap repair that can easily be completed by novice DIY’ers. If you know your spark plugs have not been replaced in that time frame it may be a good idea to knock out the repair as preventative maintenance.

5) N53 Bad Ignition Coils

Another BMW N53 issue causing power loss, misfires, and rough idles (same or similar symptoms as spark plugs).  The coil packs are usually an overlooked issue.  It seems most owners report this as the last item they replace after the injectors, and spark plugs to fix the misfires and rough idles.  While it is difficult to diagnose with certainty, getting to the coils is relatively easy; they actually sit on top of the spark plugs and must be pulled out to replace the spark plugs.   If the engine has over 50,000 miles (or if they have not been replaced in the last 50,000 miles), chances are the ignition coils may be faulty or under-performing.


Compared to other engines in the BMW lineup, I would say this engine is reliable and ready for a long life. While some of the 5 listed common problems with the N53 can be expensive to replace, none of them are so serious that they truly compromise the reliability of the engine completely. Of course, older engines with high mileage may develop oil leaks or other issues as a part of standard wear and tear, though they are not overly common issues. A fuel pump may put you in limp mode, but will not retire the car to the junkyard.  The same goes with for the injectors, spark plugs, and coil packs.

Reliability score 1-4 with 4 being the worst: 1

BMW produced a fantastic engine to make its mark as their last naturally aspirated inline-6 engine.  Let me know what you think of the engine if you own one or your experience with it.

If you liked this post, check out our article on the N63.

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  1. I own a 528 ix drive 2010 and your are correct because it appears the engine is suffering from poor maintenance issues, it has about 200,000+ miles on it and im just beginning to feel the mileage. I have it at a BMW service center for diagnostic and im looking for economical ways to repair and upgrade this vehicle. Ironically I dont think im having any of the 4 issues here but I will be doing the replacements as it is extremely helpful information and im certainly glad I found this site. So far thou I will be needing a new transfer case, Vanos solenoid, But it seems to be typical 200k mile faults.

    1. Hi Ulysses,

      Thank you for the comment! That is impressive mileage, and goes to show these N53 engines have quite a bit of life in them. However, as you stated, that is definitely a point where things may start to catch up quickly. Any issues popping up at 200,000+ are fair game as that is quite a bit of wear and tear on any moving components. The HPFP and fuel injector repairs can be a bit pricey, so you may consider avoiding those repairs unless there is a noticeable issue or fault. Then again, it can’t hurt to tackle as preventative maintenance if it’s within the budget.

      Best of luck getting your 528i xDrive running like it’s new again! We recently put about $12,000 into our 2007 335i with 113,000 miles to get it running like new again (though much of that budget included various upgrades and preventative maintenance). It’s definitely a rewarding experience to get your BMW back to where you want it.

      Best Regards,

      BMW Tuning Team

  2. I own a 523i , 2011 with mileage 125.000KM. No issues at all so far. injektors and plugs replaced onde. The 6 cylinder engine runs smoothly and quietly and feels a little luxurious combined with the 8-speed automatic.
    I hope the engine will keep on the good Work for years to come.

    1. Hi Peer,

      Glad to hear you’ve had a good experience with the N53 thus far. As you mention, the BMW inline-6 engines are well known for their extremely smooth operation and the N53 is no exception. They’re so smooth and subtle under normal driving, yet offer an aggressive feel when you push the car. Great balance all around.

      Best of luck with your N53 for the years to come.


      BMW Tuning

  3. My experience, I own a 530i M Sport, (N53 Engine, 2008 model)

    35k (2010) – Injectors and coils replaced under recall
    65k (2016) – Engine radiator and gasket housing around gearbox replaced (both leaking)
    70k (2017) – HPFP replaced – Car basically broke down, limp mode.
    80k (2018) – Drive chain replaced – massive job.
    100k (2019) – MAF replaced
    101k (2020) – Next week I’m having all 6 injectors, coils and plugs replaced with brand new parts.

    All of the above under the recommendation of the BMW dealership having plugged the car in and checked repeated fault codes. In the end, I always used the same indy garage I’ve always used, Who is absolutely top-notch.

    I’ve had nothing but ‘Engine Fault – Loss of Power’ issues with the car over the past 4 years. Each fix has made the car run smoothly for a certain amount of time (months). But the good old engine warning light has always come back to haunt me.

    Now the car is rough, very rough on idle, rough-in the morning, rough after arriving to work (about 20 miles). Rough in traffic. and stinks of petrol! All the errors when plugged in are showing various injector misfires now. Hence the reason I’m having the lot replaced next week.

    Funny thing is my mates say to get rid of the car. I can’t! Because iv spent so much on it, why would I want somebody else to benefit after replacing these past parts? Hopefully, I’ll get other 100k miles out of it.

    1. Hi Jon,

      Sorry to hear about the unfortunate issues. You’ve definitely had your fair share of the expensive ones. The N53 is a great engine, but is plagued with some similar fueling issues to the N54 with the fuel pump and injectors. The chain is an interesting one as that isn’t a terribly big issue on N53’s.

      Nonetheless, we know the feeling of not wanting to get rid of your N53 after putting the time and money into it. We went down the same road with our N54 powered 535i. The car had a 2-3 year period with no breaks. Every few months a new, expensive issue popped up. Once we committed to replacing the water pump, expansion tank, fixing oil leaks, belt & pulleys, etc we were simply in too deep. Fortunately, it ended eventually. The car has been trouble free for the last 2-3 years. However, we must admit, it still does not run quite as well as our 135i and 335i which have been much better cars overall.

      Best Regards,

      BMW Tuning

  4. I suspect the water pump next job actually. They did mention an error code relating to that too!!

    Bloody cars.

  5. Currently have a 325i m3 replica… car runs really rough only to find out my injectors where not coded properly…

    Bank 1 running
    Index 6
    Index 11
    Index 11

    Bank 2 running
    Index 6
    Index 6
    Index 6

    2 index 6 injectors leaking… one on each bank so replacing with index 11’s hopefully will solve issue. Moreover the car is in very bad shape electronically however BMW Doctor (YouTube guy) has helped me out with DME CAS And all other electric issues. Car should like a dream after

  6. My experience with N53b30 3.0 liter engine (BMW 325xi, 2008):

    I bought it in February 2019 and the dealer said there is only one major issue – NOX sensor. I convinced the seller to decrease the price for 500 eur and bought it in hopes that I will replace it and enjoy driving. At the end, I have replaced NOX sensor, all 6 spark plugs, coils, all 6 fuel injectors, did walnut blasting, changed LPFP and filter, but the car still does not go as it should. I spent about 4000 euros over the year in replacement parts, but it still hesitates and feels like an old 1.8 volkswagen engine. Now, the indie told that loss of power and hesitation may be related to bad valve lifetrs, so I dropped it off for replacement of valve lifters and crankshaft bearing shells. I really hope it will solve the issue as I don’t have an idea what might be wrong with it. To be honest, I regret buying this car, because I never knew it can be so bad and expensive.

  7. I have 2008 325i n53 manual and its a beauty. I bought it off my brother 14 months ago and he had owned it for 8 years! I did experience rough idle and stuttering throttle and loss of power after 1 month of owning the car but after i replaced the coil pack its ran buttery smooth since. One thing to be careful is cheap fuel. Give it some 95 or 99 octane and she sings. Next week ill do sparks and oil service myself. I love the linear power delivery and rowing through the gears

  8. September 2018 I bought a 2008 325i e91 (3.0l) automatic with the N53 engine. When there’s nothing wrong with the car, I absolutely love it to bits. But, it’s needed a lot of work done… Sure, I was expecting some work was needed as the car had 230 000KM on it when I bought it. I’ve racked up around 25 000KM on it since I’ve owned it and this is what has been done so far:

    – Full exhaust manifold replacement, cylinders 1-3 and 4-6, because the catalytic converter in both was shot. First the indy garage tried to burn the converters to clear any clogging but it was to no avail. Luckily I was able to find replacement parts from a shop here in Finland that sold used parts from wrecked cars, so I saved A LOT on parts. The “new” parts had less than 80 000KM on them. The work was very expensive though as the nuts and bolts keeping the old manifolds in place were completely corroded and melted into one. Also all the gaskets were ruined and had to be replaces.
    – Nox sensor on bank1 after the manifold replacement.
    – Gear lever replacement. The electrics on the gear lever were done for and the car couldn’t be put in to Sport Mode. Very cheap part from another wrecked car from ebay, Work was cheap as well as the replacement was very easy. Wire just clipped from the outside of the gearbox.
    – Valve cover gasket was leaking so it had to be replaced, also the spark plugs and coils were then changed. This issue manifested exactly as loss of power, rough idle and such.

    Other than that. I had to replace one loose trailing link and all door handles on the inside of the car because they had gone sticky as hell. I suppose someone had cleaned them with some chemical which ruined the rubber. Another big one that’s forthcoming is the profile-gasket on top of the oil pan… Again a cheap part but it takes some hours to do the work.

    So all in all I’ve poured in about 4000€ on repairs in less than 2 years, not including new summer alloys and both summer and winter tires… So all in all around 5000€ so far. Can’t say I’m too happy about that.

    I’m planning to keep the car as now at least I know what has been done and am not expecting any issues in the near future. Maybe in the spring it’s a good time to consider selling, as a rear wheel drive car with better than average power should be a desirable car for the summer 🙂

  9. Brilliant thread and has confirmed some of my issues. I have a 2008 330i e93 with a meager 36k on the clock. I’ve only owned it for 1500k and am now finding faults. I’ve recently had misfire and engine light so changed plugs and found cylinders 3 4 and 5 to be black and wet. The injector indexing is strange as it has 5 index 9 and one index 3. Also found a crack in the Cylinder head cover right next to the oil top up hole. In the process of getting new parts from BMW but I’m a little surprised they have failed after such little use. Hopefully the fuel economy will improve as 22mpg is pretty poor.

    1. Hi James,

      Sorry to hear about your unfortunate issues with such a low mileage BMW. The different index injectors mixed definitely doesn’t sound great. It’s fine if the banks (cyl 1-3 & 4-6) had different injectors but you typically want all of the same index on one bank.

      Sounds like a few of the injectors were leaking so I suspect you’ll pick up a little fuel efficiency once it’s all fixed up. Best of luck.

      Best Regards,
      BMW Tuning

  10. Im fairly certain these engines need to be ran upto temperature. If its that old with such little mileage chances are you car hasnt had much chance to warm up to normal operating temps. Maybe im just old school

    1. Its a very valid point, it does take a while to get warm and the oil temp takes a good 20+ min to get up. Do they typically take this long? This is my first 6 cylinder and my first Petrol for 10 years.

      1. Well if you want you could change your oil to castrol edge 0w30 as mine was ran like that for 4 years which definitely made things heat up quicker and i never had any temps go above 105 even on hot days with very enthusiastic driving or if stuck in traffic. Now that my mileage is over 100k ive switched to 5w30 and im changing oil at half intervals just to be extra cautious. My advise is never go above 3k rpm until oil temps are up.

  11. I have 2008 325xi N53 (3.0L, manual shift) with 160 000km/100 000 miles on it. I’ve owned it for 50 000km / 30 000 miles. Aside from replacing break housing,pads and disk on rear axel, so far no major renovations done.
    During the last year or so, I’ve noticed one behaviour with the engine that slightly bothers me. Ie. is it an indicator of some part nearing its end of life.
    Cruising with the car, nearing an intersection. Gas pedal lifted off for a good while and the car slowing down. Once at the intersection, still moving, revs below 1500rpm and now pressing the pedal in order to start accelerating again. about 1 sec after starting the acceleration, the engine stutters very briefly (0.1 sec) before continuing the acceleration normally.
    In addition, now that we had cold weather (-18c/0F) here, the car didn’t start like on the warm weather. but the starting lasted several seconds (5+) where the engine got some revs, then lost the momentum and starter kicked in, got some revs, (rinse repeat) before finally starting up with dark petrol smelling exaust cloud. IE. last and previous winter it didn’t really matter how cold the weather was. Always started like in the warm weather.

    I think the car hasn’t have spark plugs/coils/HPFS changed during its lifetime.

    PS. The engine is absolute pleasure to drive, torque even at low revs, power that comes up nice and smoothly.

    1. start with reading codes ; important for good diagnoses
      and then the spark plugs (NGK) special for the N53 engine.
      Worked for us ..
      Dealerauto NL

  12. I bought a 2009 E92 325i highline with the N53 engine on 54,000 miles in October 2020. Had it inspected twice and no issues apart from the oil pressure sensor was loose and the (I now know) dreaded NoX sensor fault. My local garage reconnected the oil pressure sensor and was fine, but the 30E9 nitric oxide catalytic converter, aging code wouldn’t go away.

    I had a Noxem alternative sensor installed + adaptation done and it fixed the problem and improved the mpg from about 32mpg on a long run to 45mpg plus on a long run. It picked up a low pressure fuel pump 2AAF code after the Noxem was installed, but am told this is a shadow code so am leaving it.

    Have also replaced the battery, spark plugs and one coil pack since buying. Overall its been a good buy, fun to rev car that looks really good with nice luxurious interior. Added an MMI unit to the CIC head unit for Apple Car play and it makes it feel a lot more modern.

    Will probably look to do a muffler delete as the engine is sooo quiet and remap the car at some point in the future, although not essential at all.

  13. Have 2007 E61 LCI, one of the first, registered in March2007, type 525i, with an N53 engine I understand . Since about 3 years I have an occasional engine fuel warning, (loss of power) and get in to limp mode, but after a restart it is gone, for months, sometimes.
    I had codes 29F3 and 30E9, but after clearing the codes they come back within half a minute.
    It is my understanding that the 29F3 means LOW fuelpressure sensor defective, and I have read that owners who replaced this sensor did no longer have complaints.
    However, thìs article indicates that the problem is related to the HIGH pressure pump, which I believe is an expensive component. And there is no reference in this article about this low pressure Sensor, which is elsewhere reported as the main culprit.
    So, what action to take? I understand that there is another replacement part for this sensor, but I am unsure about the new partnumber, could you advise please? Current mileage is about 240.000 km.
    Other than this, it is a super car

  14. I fully agree with author. I’m the lucky owner of a 5 series 530i/2010. I’ve had the issue with the injectors but other than that, flawless for all six years and 160.000km. Also other parts as suspensjon, wheelbearings and chassis seems rock solid.

  15. This has been a very nice thread to read. Very interesting to hear about some of other peoples experiences with their cars.

    I recently bought a 2008 330xi E91 with the N53 engine, and so far I’ve spent about €4000 on repairs, with 4 new injectors, a new cat and ac compressor among a few other things. Not a great start so far, but currently the car is running alright. Idle and rev is pretty stable, although I recently did have the Engine warning loss of power message. No apparent symptom but it gave me the P0015 which seems to point to the VANOS solenoids which I might have to look into soon.

    I’m really loving the car when it’s running good, so hopefully I’ll be able to get these issues sorted soon.

  16. How do you spot faulty injectors on n53b30a 2007? If you’re looking for one.

    How do you spot potential fuel pump malfunction??

    1. Hi Stoyan,

      Leaking fuel injectors can be tough to spot if you’re looking to buy an N53. You’ll usually notice a rough idle and engine misfires. When I bought my N54 335i (nearly a decade ago) everything seemed great at first. However, I changed the spark plugs & ignition coils a few months later and that’s when the rough idle and misfires really became an issue. It turned out to be two leaking injectors. Ultimately, the symptoms of the leaking injectors weren’t evident until after replacing the plugs and coils. You can pull the engine cover off and see the injector index numbers (the last number(s) after the dash) as some index injectors are more reliable than others.

      Most N53/N54 engines should have one of the newest versions of the HPFP, which are much more reliable. Most of the old designs have likely failed by now – if not 5-10+ years ago – and replaced with the newest, much less problematic pumps. Symptoms of HPFP failure include rough idle, long cranks, limp mode, misfires, SES light. It’s pretty clear something is wrong when the HPFP starts failing, so you’d likely notice after a test drive.

      A 15+ minute test drive is a good idea at the least or if you’re serious about a specific car then it might make sense to pay a mechanic for an inspection. When it comes to test driving, it’s ideal if the engine is cold and hasn’t been driven in at least a few hours. Symptoms of certain issues are more noticeable during cold starts. Drive the car until it’s up to full operating temperature and restart the engine. Park and let it sit for 15+ minutes (maybe while negotiating or asking the owner/dealer for more info and details) and then look under the car for any potential leaks. Best of luck in finding a nice, clean N53!


  17. Hi i have a 2010 bmw e91 330i msport
    N53 engine. 110,000miles

    I had noticed and suspected a leaking injector
    on cylinder 6 i had all my injectors tested and re-sealed ( index 11 injectors) the tester comfirmed the bad leak on num6. I went out to bmw and purcashed new injector not cheap! I fitted them back and got the new injector coded i didnt change my NGK spark plugs as they are only 5-8k miles since i replaces them last and now still misfire on cylinder 6 sad times.. i cleard codes then swaped coils over and spark plugs the misfire stayed on cylinder 6! Help!!!

    1. Hi Drini,

      Since you already tried swapping coils and plugs, the next place that I’d look would be carbon buildup on the cylinder 6 intake ports. If you haven’t walnut blasted your engine recently, or at all yet, it could be the case that the carbon buildup from the direct injection system has gotten so bad on cylinder 6 that it is causing a misfire. That seems consistent with your mileage if you haven’t yet walnut blasted your engine. Since cylinder 6 is the closest to the PCV valve, it likely sees more oil vapor enter the intake tract than any of the other cylinders.

      Hope this helps,

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