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Thread: N54 (135i) very high fuel trims on both banks, plus DTC

  1. #1
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    N54 (135i) very high fuel trims on both banks, plus DTC

    Hello,

    I am new here so I apologize if I am committing any faux-pas or doing anything incorrectly. I have searched this forum and a few others very thoroughly and have not found anything quite like the problem I'm having.

    The car is throwing codes P2098,P2271 (bank 2) - OR - P2096 and P2270 (bank 1), seemingly depending on whatever mood the car seems to be in that day. Sometimes it also throws P0041.

    The fuel trims are extremely high in both banks, averaging around 15% on one bank and 20-25% on the other. Depending on the day, bank 1 will be higher, sometimes bank 2 is higher.

    The codes all indicate a problem with the post-catalyst O2 sensors, OR something upstream that is confusing the ECU when it looks at the sensors.

    I have considered the following failure modes


    • Bad O2 sensors - I find this unlikely because the car only has 50k miles, and its also unlikely that sensors on both banks would start having errors simultaneously. I have also used some basic OBD reading software to view the raw voltages, and the sensors appear to be behaving properly and in normal ranges based on what I've found online.
    • Vacuum leak or intake leak - I have inspected all vacuum lines that are accessible without tearing the whole bay apart, and found nothing. I've done the 'starter fluid' trick on almost every vacuum connection, as well as around all gaskets I can find on the intake side, with no luck. Additionally, have viewed the vacuum sensors in Torque and I appear to be holding steady around -21 psi, which seems to be normal.
    • High Pressure Fuel Pump Issue - I can directly view fuel pressure using Torque, it holds steady around 700 psi at idle and jumps up around 2000 during WOT. From everything I've read, this is normal operation.
    • Exhaust Leak - have done a pretty thorough inspection and can't find anything.
    • Dirty or bad Injectors - I have run some injector cleaner through the fuel to no avail. Unfortunately I don't feel super confident in removing injectors myself to inspect them.


    I'm at the point where I think I've reached the limit of what I can investigate myself, and I am planning to go to the dealer. Before I did this, I figured I would ask here if anyone had any ideas that I hadn't considered. Mostly I'm scared that the dealer is going to charge me the $200 diagnostic fee and then just tell me to replace the O2 sensors because that's what their sheet says, which I really don't think are the problem.

    Extra question - does anyone have any recommendations for any true BMW pros in the Los Angeles area? I am closest to the Santa Monica dealer but don't know much about anyone in the area (I just recently moved here). I really want to find someone who will do real diagnosis work instead of trying to throw parts at the problem for $$$, which is a problem I've had with dealers before.

    Thank you all in advance for reading and for any help you may be able to provide!

  2. #2
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    Welcome maximillius. Sorry, I don't know anything about the N54, but since you are posting with "P" codes, I'm going to guess that you are using some flavor of generic diagnostic scanner. I'd suggest that you invest in some sort of BMW specific scanner, which will be capable of providing much more detailed information about your car.

    Many here use a generic cable purchased from ebay along with a laptop and software, such as INPA. There are also several handheld alternatives. I use a "Carly" which is a wifi adapter that works in conjunction with either an android or apple device. I recently also acquired a Foxwell NT510, which has the added benefit of some coding and the capability to reset adaptations. There are many out there and they vary in what they can do, but in terms of diagnostics just pick one. BMW fault codes are much more specific and will usually point you directly to the problem.

  3. #3
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    Welcome to the forum.

    +1 to Tony's advice; using an OBD code reader really isn't in your best interest. That Foxwell unit Tony has recommended looks excellent....(Tony, maybe post that link again here?)

    Now, all I've got are those P-codes.....I don't trust them, but that's what we have.

    So, we have both post cat sensors telling us they're running lean. And then we have both sensors telling us they're stuck lean......and, we have a code telling us that those two sensors are swapped.

    So first: Does this car have a performance-related software reflash, or any other performance mods?

    Second, I'd likely put the car in the air, bring up O2 sensor data , and then unplug one post-cat sensor, and make sure that the scanner's data disappears on the correct bank. (Bank 1 is cyls 1-2-3, Bank 2 is 4-5-6). If not, swap plugs on those sensors from one bank to the other, which might fix your issue, if indeed the sensors are swapped..

    Third. I'd have to hook the car to ISTA-D, do a guided test plan for those codes. And then I'd maybe reflash to the newest software, using ISTA-P.....unless of course, you have a custom tune you're trying to preserve.

    A HPFP issue throws codes for HPFP. Intake leaks will give you codes for several places in the airflow, prior to the post-cat sensors.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  4. #4
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    You might have to pay more than 200.00 to diagnose it, check the spark plugs if there black it could be the injectors welcome to the world of the high pressure direct injection engines

  5. #5
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    Hi all,

    First off thanks for all your advice!

    It's been a bit of a ride since I posted this.

    First I took it to an independent mechanic who performed a smoke test (finding nothing), checked the functionality of the 02 sensors (they appear to be working and switching fine, and they were not misplaced) and reset fuel adaptations. Resetting the fuel adaptations appeared to mask the problem for awhile.

    I then had my HPFP fail rather suddenly, and replaced it as well as the low pressure fuel sensor, under the extended warranty.

    I then had my intake valves cleaned (they were nasty!)

    HPFP replacement + intake valve cleaning had the car feeling smooth as butter. Felt like it drove a million times better than ever before.

    However, shortly after returning home from intake valve cleaning - the lean codes returned! (this I think makes sense. resetting the fuel adaptations had set the 'normal' a little lower, and cleaning out the valves suddenly caused the engine to get more air, flipping the mixture lean enough to set the codes again)

    Took it back to independent mechanic. Found a crack in the valve cover. Replaced valve cover, reset fuel adaptations. Like before, this masked the problem for awhile, but today the lean codes returned during a long drive back from san diego. I even experienced a little bit of sputtering at low RPM, which didn't feel great. Fuel trims still way too high to be normal.

    At this point I'm super frustrated and at the point where I'm willing to just replace everything. I found a good price on a full set of fuel injectors so I just ordered those today. If that doesn't work, I'll go against my better judgement and replace all the O2 sensors as well. Failing that, the ECU...

    People told me BMWs will cost a fortune in maintenance... I didn't realize how quickly I would have to learn this lesson! I'm open to any other suggestions as to what else could be wrong...
    Last edited by maximillius; 06-19-2017 at 01:24 AM.

  6. #6
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    Yes ,a NA BMW will cost much less to maintain than a Forced Induction variety.
    "Choosing the correct shop is as important as the correct diagnosis

    Former owner of a Red RL411 wannabe owner of pictured vehicle

  7. #7
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    Um, just so you know, those new injectors need to be programmed into the computer, using the last digit after the part number, and a BMW ISTA computer.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  8. #8
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    Try www.bimrs.org to find a BMW shop in your area. Also, ask for shop recommendations from members of the local chapter of the BMW Car Club of America. Google "BMWCCA #####" where "#####" is your zip code.

  9. #9
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    Are you proficient with computers? Just at an OK level. Do you have a Windows laptop?
    -Abel

    - E36 328is ~210-220whp: Lots of Mods. RomRaider self-tune work in progress.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg: Many Mods ~300ft/lbs tq, diesel, daily beater. Love/Hate relationship.
    - S52 Estoril M Coupe

  10. #10
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    The lower end models aren't that unreliable, and if taken care of, they can be quite OK. Yours seems to have been neglected or someone was trying to dump their problems onto the next person.

    Stick around and listen to the guys here, as you can get this fixed with maximum efficiency. The free help here is actually some of the best. I can help you get some basic BMW diagnostics set up, so that way you can easily run diagnostics yourself. If you have any kind of Windows laptop, it would only cost you about $20 for the cable.
    -Abel

    - E36 328is ~210-220whp: Lots of Mods. RomRaider self-tune work in progress.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg: Many Mods ~300ft/lbs tq, diesel, daily beater. Love/Hate relationship.
    - S52 Estoril M Coupe

  11. #11
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    Thanks all for the continued replies! I'm aware the injectors need to be coded to the vehicle. I am proficient with computers and I'm confident that I could figure out the programming with a little guidance. However the problem really is space and time. I live in an apartment complex with underground parking, and they frown on doing car maintenance down there. I get away with doing some basic bolt on stuff because I'm friendly with the ownership, but I definitely have no way to get the car up in the air or on stands.

    The independent mechanic I have been seeing is a BMW/Mini specialist, and they have all the required tools and access to BMW systems.

    Typically I am willing to spend the money to have a professional do the work, but I want to make sure that what they're doing makes sense to me and I'm not needlessly throwing money away (I'm an engineer, so not knowing exactly whats going on will always keep me up at night).

    I can help you get some basic BMW diagnostics set up, so that way you can easily run diagnostics yourself. If you have any kind of Windows laptop, it would only cost you about $20 for the cable.
    That would be awesome - thank you! What cable would you recommend? When I was exploring the option of setting up a diagnostic laptop the cables I was seeing were definitely more than $20, but maybe I was looking in the wrong place.

  12. #12
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    So here's where I'm at currently. The problems could be -

    A) Unmeasured air is getting into the cylinders.
    - This seems unlikely because the N54 uses an absolute pressure MAP sensor right on the intake which should capture everything going into the engine, unless there is a gross leak around the intake manifold that is creating some turbulence in the manifold and not getting an accurate pressure reading
    - Smoke testing has been completed on the intake side of things with no findings

    B) Fuel delivery issue
    - HPFP already replaced
    - LPFP exonerated by dealer test plan during service
    - Pressures look good at all times
    - Injectors seem to be the only remaining possibility

    C) Sensor issue
    - O2 sensors appear to function correctly when watching voltages throughout various conditions (both WOT and idle) Also seems unlikely that they would fail at only 57k miles, and also unlikely that they would fail on both banks. Also unlikely that they would fail with only a slight offset - I would expect them to rail high or low.
    - MAP sensor faulty. Like above, only 57k miles, I find this unlikely. I removed, cleaned, and replaced the existing sensor once already.

    D) ECU issue
    - The most unlikely thing I can think of, I would tackle this last

    Based on the above I think I want to tackle the injectors next. Does that make sense to you guys? Would you approach this differently?

    - - - Updated - - -

    Hm, I had a second reply written up about the cable and injector coding but it looks like it didn't submit.

    Short answer yes I am proficient with computers and I absolutely would welcome any advice on how to get a proper diagnostic system set up. For the injectors I would probably lean towards having a professional do the coding because I wouldn't want my first foray into programming to be something so critical!

    Thank you all for your continued replies, this seems like a great community.

  13. #13
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    Coding injectors is easy. Impossible to mess up really.


    You need this cable http://www.ebay.com/itm/192031744804


    And this pack I put together here https://www.bimmerforums.com/forum/s...xperimentation


    Yes I know it's targeted for Z3, but it'll work with your car, when using E90 profile. Ignore the Z3 specific cables and use the linked one above or similar. If choosing similar, get one with green mainboard.
    PM if you need specific help.
    -Abel

    - E36 328is ~210-220whp: Lots of Mods. RomRaider self-tune work in progress.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg: Many Mods ~300ft/lbs tq, diesel, daily beater. Love/Hate relationship.
    - S52 Estoril M Coupe

  14. #14
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    OK, you've inspired me - I bought the cable and a cheapo laptop and I'll give it a go. Awesome pack you've set up there, thanks man.

  15. #15
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    Abel's the best ! When I have BMW computer issues, he's the guy who fixes the problems for me. He's done many things with BMW computers that are supposed to be impossible, to help me, and the shop where I work.

    Thank you again, Abel, for all the wisdom and generosity you share with the members here! (And me, especially)

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  16. #16
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    Car has started intermittently stuttering under throttle and also has a rough idle at times. Feels kind of like misfires but not quite so violent as if a spark plug had failed.

    At this point I'm getting more and more confident that injectors are my issue. I'm going to stop driving the car and wait for parts to arrive and get this done. Going to replace all spark plugs and coils while I'm at it. Will report back with results!

    Thanks all for the assistance
    Last edited by maximillius; 06-21-2017 at 12:11 PM.

  17. #17
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    Hi all,

    Successfully got 5 injectors out. The 6th is stuck in there good. Going to purchase the special slide hammer tool before I continue.

    During an attempt to install 2 new injectors I sheared off the screw that fastens the hold-down bracket. (I'm pretty much retarded. I don't know what I was thinking).

    Going to attempt removing the sheared bolt with a screw extractor, but I'm going to need a replacement bolt.

    Does anyone know the size or part number of that bolt so I can buy a new one? (or where I could find that information?)

    Talking about piece 7 in this image

  18. #18
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    If you are careful you can use two pry bars to pry out the injectors instead of spending money on the slide hammer- but the slide hammer does come in handy.

    Also- do not use the nut and hold down bracket to push the injectors down into the cylinder head- as this does not seat them all the way down and I have seen injector bores become ruined and then the engine needs a new cylinder head. Instead use a long flat head screwdriver and put it on the alignment tab (at the bottom of the injector that slides into the cylinder head) and tap it down with a hammer until the injector is seated all the way down.

    As for the broken bolt I would go to the dealer and buy that specific bolt. Will only be a few bucks and it's the only thing I would trust.

    From what I see it sounds like injectors though- as long as the last two numbers of your injectors were under "11" , the new injectors you get should have the last two digits as "12".
    11 and 12 are good updated ones. Anything under 11 are old bad faulty ones that BMW replaced and re engineered.

  19. #19
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    Yup, I had several injectors that were still index 7 and they were mixed with a few index 11 in the same bank. One was also coded improperly. A real mess.

    My new set is all index 12, can't wait to have them all in properly...

    Thank you for the advice on seating the injectors. I was definitely doing that wrong.

    Do dealers usually stock small hardware items like that? That's definitely the easiest thing if they keep them around. Would be nice to have a part # for it though, so far google hasn't helped..
    Last edited by maximillius; 06-28-2017 at 01:29 AM.

  20. #20
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    #7 I believe is what you're looking for:http://www.realoem.com/bmw/enUS/show...diagId=13_1182
    Last edited by MIKYZZ4; 06-28-2017 at 01:52 AM.
    "Choosing the correct shop is as important as the correct diagnosis

    Former owner of a Red RL411 wannabe owner of pictured vehicle

  21. #21
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    Yea, especially if they were mixed with index 11 that's a big part of your issue. Definitely needs the injectors done either way.

    Also the dealers can have stuff next day for you, just call them and have them order one and pick it up the next day if they don't have it in stock. A lot of times they have random nuts and bolts like that in stock though. You may get lucky!

    Let us know how it goes

  22. #22
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    Amazing, thank you - somehow I've never seen RealOEM before. That's so useful.

    Unfortunately I will not be able to tackle this for awhile because I'm about to depart on a business trip followed by a visit to see some family. Will order everything I need and be ready to take care of it after the 4th.

    Thank you all for being so helpful and not laughing at me when I overtorque an obviously bottomed out bolt enough to shear the damn thing...

    Does anyone have any tips/tricks for using a screw extractor / EZ-out? I understand the idea (our techs use them all the time at my job), but I've never had to do it myself before.

  23. #23
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    You could first try using a punch or pick tool to rotate / unscrew the fastener.
    Also use penetrating oil to loosen up the fastener.
    I used an extractor on some of my car's transmission pan bolts.
    I think the idea is the drill out the center of the fastener, then use the extractor.

  24. #24
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    I stopped using screw extractors years ago. They are very hard and brittle, so it is easy to break one when trying to extract a screw. Sometimes a carbide drill will drill a broken "easy out" out, but frequently even that won't work. If part of the bolt sticks out and if possible I'll TIG weld a nut onto the stub. Otherwise I use left hand twist drills. Start by making a light pin prick as centered as you can and if that looks good, deepen punch mark. I usually start with a left hand drill about half the diameter of the bolt. Frequently as the drill gets about half way or more into the bolt it will unscrew. If that doesn't work I'll try a larger drill slightly smaller than the bolts's minor diameter, which may unscrew the bolt. As a last resort I'll drill out the bolt and use a Helicoil or Timesert. A Helicoil works well in a blind hole, but not as well if the hole isn't blind.

    In the case of rusty fasteners, PBlaster or Kroil and time will be helpful. By time I mine hours, or if possible repeated applications over a day or more. When feasible, a flame wrench is helpful, meaning an oxy-acetelyne torch as it can apply high heat precisely.

    A interesting tidbit. You can burn a bolt out of a cast iron part without damaging the threads. I learned that one from a tractor mechanic many years ago. Farm equipment has lots of castings and is frequently exposed to water, which frequently rusts the bolts.

    While I'm on a roll... An easy way to deal with a frozen brake rotor retaining screw when the hex socket strips is to pick a drill the same size as the bolt's major diameter. As soon as you drill through the head of the bolt the rotor will come free, leaving enough of the bolt to grab with vice grips. Then it becomes a matter of using penetrant and possibly the flame wrench.
    Last edited by thejlevie; 07-01-2017 at 11:05 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  25. #25
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    I believe the broken bolt involved here is aluminum; that's why it broke so easily. They should not be reused, by the way. However, that means it will be very easy to remove. Most likely, you can just twist it out with a pair of needlenose pliers. M7 is pretty small to have to drill, so if you do, you need to use the punch and reverse drillbit just as Jim has advised above.....but it will be very easy to punch and drill the soft aluminum. That said, aluminum bolts pretty much always spin right out.

    Um, if the injector seals are out of their sleeves for any amount of time, they will expand, and need to be replaced before installation.
    Last edited by bmwdirtracer; 07-02-2017 at 09:14 AM.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

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