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Thread: MAF Sensor info....

  1. #1
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    MAF Sensor info....

    How to test the MAFs yourself and How MAFs work.

    The MAFs are vital to the proper function of the S62 engine. The engine can never work better than its MAFs.

    The MAFs (Mass AirFlow meters) are located in the M5 and Z8 air intake tubes. The MAFs report to the Engine Electronics (DME aka ECU) the amount of air that is drawn into the engine, and what temperature this air is. The DME uses this to calculate how much fuel to inject.

    Vital as the MAFs are, those have to be _really_ bad before you actually get a stored fault-code.

    The functional test by the BMW tester just tests the MAFs at idle with the car standing still. IMH experience that says absolutely nothing about how they perform at WOT (Wide Open Throttle).

    I think there is an economical (warranty) reason why BMW does not want the MAF fault code to trigger as soon as the MAFs start to be less-than-perfect, rather than only when there is extremely poor MAF function.

    MAFs typically last 50000 miles before getting so contaminated it affects S62 engine performance.

    There are two methods to test the MAFs yourself:

    Method A - using the instrument cluster of the car *********

    Read post #11 in:

    http://www.m5board.com/vbulletin/showthread.php?t=1898

    Follow those instructions, and select the mode for fuel consumption per hour.
    With the engine fully warmed up, drive several WOT (wide open throttle) accelerations. Notice the fuel flow per hour numbers. If everything is ok the numbers should increase continously to about 140 litres per hour at WOT at 7000 RPM. (don?t worry about bouncing into the rev-limiter)

    The fuel-flow is directly proportional to the MAF reading reported to the Engine Electronics, so if the Fuel-flow is correct, the MAFs are most likely correct too.

    Method B - using an OBD-II scan-tool *******************

    1. Get a graphing and data-logging OBD-II scantool. If you already have a laptop PC, it will cost you about US$ 100 to buy one. Worth every cent. (I use the one called "ISO" from www.obd-2.com which I am very pleased with)

    2. Plug it into the car and go for a drive

    3. Look at the graph for CLV (calculated load value). This is basically the MAF signal expressed in percent of the expected maximum at each RPM.
    When you accelerate WOT this number should immediately go to 100% and stay there until you release the throttle or hit the rev-limiter .

    4. If the CLV reading it is low at all RPMs, try new air filters.

    5. If it is ok at low RPMs, but lower at higher RPMs, try the MAF cleaning procedure and the retest immediately. If this improves the numbers you know 100% there is (or if the cleaning was very successful used to be) a MAF problem. This does not say it is the only problem, but the car can never run better than its MAFs.

    Symptoms of bad MAFs ************************

    In degree of malfunction of the MAFs possible symptoms are:

    High Lambda values at idle (lean air-fuel-mixture)
    Engine hesitation at high RPM
    Engine misfire at high RPM
    Engine going into limp-home mode at high RPM

    MAF cleaning procedure ************************

    http://www.louv.tv/cars/m5/MAF/
    (by m5board member Louv)

    How the MAFs work ***************************

    The MAFs have a non-heated temperature sensor and heated temperature sensor. The latter is made of a very thin wire of platinum metal. The wire is heated to about 200 deg C, and its temperature is continously monitored and the heating current is controlled so as to keep the wire at this temperature. The more air that passes the wire on its way into the engine, the more the wire will be cooled. The electrical current needed to maintain the sensor wire at 200 deg C, is directly proportional to the amount of air that passes it, and also depends on the temperature of the air (hence the non-heated temperature sensor).

    The electrical current and the air temperature are measured, and the corresponding air-flow is calculated and reported to the engine electronics.

    How MAFs clean themseves ***********

    Once in a while the MAFs will run a very high electrical current for a few seconds through the platinum sensor wire, so the wire gets red-hot (1000 deg C). This burns off much of the contaminants, and probably help keep the MAFs working much longer between manual cleaning or replacment intervals.

    How MAFs fail *********************

    With time the MAF platinum-wire gets fouled with contaminants settling from the rapidly passing intake-air. These contaminants acts as thermal insulation on the wire. The effect is that the wire will not be cooled as much as it should by the air-flow, and thus reports too low air-flow to the engine electronics. The engine electronics in turn uses this too low air-flow number when calculating how much fuel to inject. The fuel injection will be to low, and the air-fuel mixture in the cylinders of the engine will be lean.

    NB: Many M5 owners have reported K&N oiled intake air filters to cause MAF contamination.

    Warranty *************************

    As the MAFs influence the air-fuel mixture and cause high Lambda values (lean mixture), it is possible to fail emissions testing due to non-perfect MAF sensors. When the vehicle fails emissions testing the Emissions Components Warranty may be applicable.

    In the USA see:

    http://www.epa.gov/obd/warranties.htm

    The mandatory warranty covers everthing relating to emissions for the first two years, and the OBD, ECU (DME in BMW language) and the Catalytic converters for eight years.

    So in the US the MAFs are covered for at least 2 years by law, but not for eight years.

    David

  2. #2

    MAF - further info...

    There is now an easy clean solution to help keeping your MAFs from getting contaminated. Even if your car sits they get a layer of residue on them, just like the windscreen does, and this will make your motor run richer, which in turn may increase your chance of sufferiing the dreaded S62 Carbon Build Up Issue.

    MAF Cleaning Solution link.


    and here is some more MAF info:

    MAF Test proceedure for M5's
    David, I have no idea if this will work, as the Z8 doesn't have any kind of onboard computer that I am aware of, it is limited to a tach, speedo, a few warning lights and a navigation system that gives you written directions & external temperature readings thru/on the radio, not in a dedicated screen.

    However the OBDll tool you mentioned, and also the one reviewed by Grease Monkey here, should be able to pick up the signs well enough. From reading the M5 posts it looks like heavy use will render the MAF's 'done' at 50K, but I think that as most Z8 see less than 10K miles a year, the issue for our cars will be ambient residue build up, like you find on your perfectly polished windscreen after the car has sat for a while.


    Below is the M5 test proceedure for everyones information - but our cars do not share the same instrument panel, so it is not relevant as a guide, just as comparative information:

    As promised, here are the instructions on how to get to the "Test Modes" of the OBC. I didn't run into any trouble, but as always, do this at your own risk :-) BMW apparently doesn't want you to play with this, so most modes are locked. Once you unlock them, they remain unlocked, until you bring in your car for service, or explicitly lock them yourself.

    UNLOCK PROCEDURE:

    1) Key to ignition pos 2 (no need to start engine).
    2) Fasten the seat belt to get rid of the "Fasten Seat Belt" message.
    3) Press the right button on the instrument panel, and hold it until "TEST-NR. 01" comes up (5 to 10 seconds).
    4) Press the left button on the instrument panel, and the vehicle id comes up (last 7 digits of VIN).
    5) Add up the last 5 digits to get the "unlock code", e.g. the unlock code for "AB12345" would be 15 (1+2+3+4+5).
    6) Repeatedly press the right button until "TEST-NR. 19" appears.
    7) Press left button -> "LOCK : ON"
    8) Repeatedly press left button until "LOCK : xx" appears, where "xx" is your unlock code.
    9. Press the right button. All modes are unlocked now.

    NAVIGATING BETWEEN TESTS AND PERFORMING THEM:

    - Follow steps 1) to 3) of the "UNLOCK PROCEDURE" to enter test mode.
    - Use the right button to step from test to test.
    - Press the left button to enter a test and cycle between modes within a test.
    - Press and hold the right button to exit test mode (turning the key to 0 works as well).

    Here is what I know about the various test modes:

    2) Instrument test: Cute light show in the instrument panel. Ever wanted to see the speedo show 190 without having to leave the garage?

    3) Don't know.

    4) Current fuel consumption in liters per 100 kilometers and in liters per hour.

    5) Average fuel consumption in liters per 100 kilometers and range.

    6) Current fuel levels in left tank, right tank, and total.

    7) Engine temperature (not sure where measured), engine RPM, and outside temperature.

    8) Current speed in kilometers per hour.

    9) Battery voltage.

    10) Country.

    11) Don't know.

    12) Not sure what these are. Could be average speed used to calculate arrival time for distance to destination set in OBC?

    13) Sound test. Goes through the various gong sounds.

    14) Don't know. Could be some diagnostic codes.

    15) DOn't know. Looks like a real-time readout of some registers.

    16) Oil temperature. I sometimes get a bogus -48 degrees C when the engine is not running. Corrects itself when the engine is on.

    17) Don't know.

    18) Doesn't do anything.

    19) Locking & unlocking of the test modes.

    20) Don't know.

    21) Don't know. This test asks you "RESET?". Let me know what it does, if you're brave enough to try it. I'd recommend to stay clear, though.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  3. #3
    This is the lastest MAF thread from our friends over on the M5 Board.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  4. #4
    DSC Off 1mean3's Avatar
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    MAF Replacement/Cleaning

    I am replacing my MAFs (bimmerworld kit) as I have had some of the textbook issues under full load.

    What has the experience been regarding the MAFs? How many owners have replaced them? Does the cleaning process work?
    I ask because there seems to be some controversy.

  5. #5
    I have never tried replacing or cleaning them so can shed no light on this, but as they are relatively inexpensive if you get the cores alone I'd say just replace them.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  6. #6
    Team Z8 KenZ8's Avatar
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    Just had it done

    I've just had the MAF's replaced (21K miles, 2002 Z8) under the extended warranty after they threw a code and tripped the check engine light. Big difference after replacement- you don't seem to notice the gradual degradation in their function.
    I've also been warned that the cleaning process can leave chemical residues which will (can?) contaminate the O2 sensors.

  7. #7
    I've noticed my car feels a bit sluggish, despite having only 12,000 miles on the clock, so I'm wondering if the MAF's might not be susceptible to a residue build up over time especially with limited use. Although I do two to three thousand miles a year thats all done in around twenty driving days, so my car is sitting a lot of the time. The windscreen seems to get a residue after a few weeks, and I always put it away polished and freshly sparkling.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  8. #8
    DSC Off 1mean3's Avatar
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    There is a lot of info on the M5board about the MAFs and how performance deteriorates if they get dirty. I experienced some hesitation and missing under throttle so I had the car checked out by my dealer.

    The error codes pointed to the MAFs. Evidential they could see the units were at their limit of adapatibility. They see a lot of M5s with this problem and mentioned that I will see a hugh difference once they are replaced.

    There is a lot of discussion about the cleaning of them as some people have experienced 3-5 replacements. The cleaning is debatable as it didnt work for all and some didnt feel they got "as new" performance onced cleaned.

    There are a lot of M5s and of course the M5 guys have a lot more miles on their cars so I think the experience is well documented on the site.

    I am replacing them today. I will let you know my results.

  9. #9
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    New MAF put in today at the dealer....thanks to this thread for all the info....$1300 labor parts ect. 2001 w/24k miles. Runs like new and not doggy at plus 4k rpm as was the case before repair.

  10. #10
    Z8 Addict Z8doc's Avatar
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    well, I am not sure what to do...

    My Z8 has 50k miles now and early on, had some hesitation issues but none in a long time. That being said, my code reader does not have any faults that would suggest the MAFs are bad and the Z8 still "seems" pretty "spirited" but since this condition appears to degrade performance slowly and I have nothing to compare to (i.e., another Z8 in the garage like someone I know), how should I proceed? Not sure I want to do a $1300 repair and replace the MAFs if they really do not need it but what would you all suggest?
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  11. #11

    New MAFs

    50k miles is really alot on 6-9 year old original MAFs, even if they haven't thrown a code. If you are even slightly handy with a wrench, you can replace them yourself for only $345 for the pair. Takes 15 minutes, tops. Even quicker if you have a 5 pt Torx bit.

    http://www.bimmerzone.com/performance_MAFS.htm

    Tyler

  12. #12
    If I understand the situation correctly, time is just as much a part of the problem as miles. Residue just builds up on them over time, even if the car sits, and that is what throws them off, so I'm now replacing mine at the same time I replace my batteries, every four to five years regardless of miles.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  13. #13
    DSC Off 1mean3's Avatar
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    Thumbs up

    I replaced mine myself. I purchased the kit thru www.bimmerzone.com for $345.00 for the pair. Very easy, 10-15 min.

    The Torx wrench came with the sensor kit. I received immediate results.

  14. #14
    Z8 Addict Z8doc's Avatar
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    Question Well, I am not sure what to do...

    I bought the MAF kit from BimmerZone including the #6 Torx wrench that comes with it. However, that wrench will not fit the tamper proof screw head. It appears to be the correct size as far as I can tell but these tamper proof screws from BMW have a male / female design and the male post inside the center of the screw is too large for the hole in the included Torx wrench ? Any suggestions? I have contacted BimmerZone but not heard back from them yet.

    Anyone know where you can buy these type of torx drivers? The Craftsman set do not have this design. Suggestions appreciated.

    PS: my Z8 is a 2003 with build date 9/02. The BimmerZone website states that the #5 may be needed on later models but they do not sell supply that one. A #5 is smaller than the #6 so I doubt that would be the problem but honestly, not sure about these tamper proof ones.
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  15. #15
    I just bought a dynamite tool kit for my bike from here, that should have everything you need.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  16. #16
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    Jeff,
    Replaced mine 1 month ago. Got the 5 point security torx here: http://www.tdiparts.com/catalog/prod...c5a9773e32bbe9

    Worked well. They had to back order, so it took about 2 weeks for it to come in. Probably have them in stock now.

    If you are coming to Dallas this weekend, let me know and I'll bring the appropriate tool. We can have a quick tech session and get you back to runnin' good.


    Mark

  17. #17
    Z8 Addict Z8doc's Avatar
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    Hey Mark, No luck here at home. I will be in Dallas so if you do not mind, bring the torx tool you have and we can swap it out then. Thanks !!
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  18. #18
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    Will do, see you there. Will be nice to put a face to a name.
    Mark

  19. #19
    Administrator thegunguy's Avatar
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    The bit is called a Torx-Pin. You can order them form lots of places.
    thegunguy

  20. #20
    Z8 Addict Z8doc's Avatar
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    Hi Mark,

    Quote Originally Posted by MarkZ8 View Post
    Will do, see you there. Will be nice to put a face to a name.
    Mark
    No need to bring your 5 star tamper proof torx bit, I ordered one from where you suggested and it came in today.

    Got the job done but.... took way longer than 15 minutes !! While removing the second (bottom) screw from the MAF, that stupid torx bit dropped down and ended up inside the engine cover pan on the bottom of the car. Now that is one tight space and since I do not have one of those small snakes, I could not retrieve it so... to the dealer I went, right at closing, and the mechanic took off the bottom cover pan and pulled it out for me. Total job, a little over an hour and a half including driving to and from the Service department to retrieve the bit (did the MAF install while with my mechanic). If anyone else is going to attempt, I suggest putting something under the MAF you are working on to catch the torx bit or the screw if you inadvertantly drop it like I did, so as to avoid having to remove the pan to retrieve it. If I had a lift or jack, could have done it myself -- looks like one more thing I have to buy -- oh, darn!

    BMW of Tulsa was great though, stayed after hours and did not charge me for the rack or time to do it. Great Service from a great company for sure.
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  21. #21
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    Thanks for the heads up. You'll be pleased with the new MAF's. Fantastic service from the Tulsa BMW folks. The jack from my E39 has come in handy with the Z8 many times. Ever dropped any screws or bits on a femur fracture ORIF? At least your car won't sue...
    Mark

  22. #22
    Z8 Addict Z8doc's Avatar
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    Just to tell you...

    Hard to tell about the new MAFs though.... I just earlier this week did the Conforti Shark Injector for the s62 engine which based on the true scientific method "seat of the pants feel"... it was a definite improvement so when I added the MAFs, less noticeble change. The Shark however, so far,!!
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  23. #23
    Sport Button On - DSC Off Lupin's Avatar
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    I keep having the engine light cominig up, BMW is getting the error "lambda sensor", (is that the MAF?).
    They said that because of little use of the car, I may need to replace the sensor beacuse they are probably dirty, or maybe the "Catalytic converter"...

    I am a bit confused, and I don't want to replace them without being sure about it.
    Theu also told me that maybe the 2 black hose in front of the engine are maybe old and the curve they make going into the engine is suffocating the engine..
    Any idea?
    thx
    Luigi
    Luigi
    2001 Z8 Black-Red

  24. #24
    I haven't heard of lack of use hurting the MAF's, but the O2 sensors (also called lambada sensors) do seem to go bad pretty easily, I'd suggest starting with those.

    http://www.lambdasensor.com/main/bmw1.htm
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  25. #25
    Team Z8 ZMates's Avatar
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    Quote Originally Posted by Lupin View Post
    I keep having the engine light cominig up, BMW is getting the error "lambda sensor", (is that the MAF?).

    Luigi

    No, it's not the MAF. The lambda sensors are the sensors plugged into the exhaust.
    Silver/black
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  26. #26
    Sport Button On - DSC Off Lupin's Avatar
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    thank you guys
    Andrew that website is great , I think here in Switzerland they wanted to charge me about 500$ each sensor
    I keep you informed
    Luigi
    2001 Z8 Black-Red

  27. #27
    Z8Mania
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    Last time around when I was far out of warranty I "complained" to the dealer- more like I said- somethings not quite right- and they said it was the MAFs and they gave me new ones gratis... speaking of customer service.......