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Thread: Running 92’ E36 Without MAF Plugged In

  1. #1
    Join Date
    Dec 2017
    Location
    Mount Vernon, Wa
    Posts
    2
    My Cars
    1992 BMW 325is

    Running 92’ E36 Without MAF Plugged In

    So my MAF has gone bad on my E36.
    It’s a 1992 325is Automatic. It’s the non vanos engine. It seems to sputter, have lack of power, and a rough idles. Have tried the MAF cleaner sold at local auto parts store, still didn’t solve the problem. But once the MAF is unplugged it runs flawlessly. My question is how long can I drive it without the MAF plugged in? What kind of damage will it do, if any? Thanks again.

  2. #2
    Join Date
    Jun 2005
    Location
    New England
    Posts
    25,402
    My Cars
    F90 M5; E36 M3 Turbo
    It will just run rich as a default. Not all the inputs to the ECU are available without the MAF, but it still has throttle position and during lower load conditions, 02 sensor. The IAT does not do anything most of the time and the coolant temp sensor is just for cold start. I went on a 500 mile trip once with the HFM disconnected. Still, I’d try to borrow a good one to test with and then buy one ASAP if that is the problem. Just because the car suddenly runs better with the NAG disconnected does not necessarily mean it is bad. It might be but the problem could be something else that is making the motor run lean.
    Last edited by pbonsalb; 12-17-2017 at 05:31 PM.

  3. #3
    Join Date
    Dec 2013
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    Chicagoland area
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    EXOTICS
    Check for a major intake leak.
    Continued rich mixture will clog cats with fuel,
    leading to cat failure and need for replacement of cat(s).

  4. #4
    Join Date
    May 2015
    Location
    Spearfish SD, USA
    Posts
    514
    My Cars
    94, 318i W/M50TUB25
    Test your MAF with a Digital volt meter the specs are listed in the bentley manual, your car has a Hot Wire MAF which is Analog the voltage it outputs corresponds to airflow on a linear scale. It is highly unlikely that it has failed because these types of meters are very durable, chances are you have a different problem all together or theres a wiring problem between the MAF, battery and ECU. you can do a test to see if the filament is good by having a partner turn the car off while you look into the MAF the wire should get red hot for a few seconds after shut down this is to clean the wire of any oil/debris before its next startup, if it doesn't light up its either burned out and needs to be replaced or it isn't getting power or ground. Personally i would be looking for a fuelling issue or a vacuum leak.
    pinout.PNG
    Last edited by snow663; 12-21-2017 at 10:39 PM.

  5. #5
    Join Date
    Dec 2017
    Location
    Mount Vernon, Wa
    Posts
    2
    My Cars
    1992 BMW 325is
    Okay so once the new sensor is installed, how do I “ reset “ the computer? I was told that’s what had to be done so the car can adjust to the new sensor... I’ve looked online but majority of videos are not for the same car. Do you just disconnect the battery terminals? Or is there a specific way for this to be done.

    Thanks in advance.

  6. #6
    Join Date
    Jul 2011
    Location
    Arlington, VA
    Posts
    9,933
    My Cars
    2018 BMW M240i
    The engine computer (DME) doesn’t need to be synced with the new MAF. Just install it and plug it in. What brand is the new MAF?

  7. #7
    Join Date
    Aug 2018
    Location
    US
    Posts
    1
    My Cars
    1992 325i sedan
    I'm having the same issues. Sputtering under load but once I hit highway speed it's a nice smooth ride. On the other hand tho, sometimes it just runs perfect. I'm confused on what to do. This is my first BMW.

  8. #8
    Join Date
    Dec 2013
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    Chicagoland area
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    4,372
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    EXOTICS
    Since this is your first BMW, learn about them, how? you ask,
    by purchasing a Bentley manual and reading through it.

    There is an immense amount of info here and a multitude of BMW websites.
    We are also here to help when we can. Btw, it is preferred that you start your own thread.

  9. #9
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    I will move the thread to the E36 forum
    Shogun tricks and tips for the E32 series are HERE!

  10. #10
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    I have the feeling that running without MAF won't damage anything. As long as the engine, intake, exhaust manifold, exhaust, cams, etc. are all stock, it should run flawlessly.
    Without MAF connected the DME will change to a complete different operation mode, called Alpha-N, using the TPS angle (Alpha) and the RPM count (N). The DME continuously looks up in its tables how much fuel to inject and when to ignite the mixture based on these two variables. It no longer meassures the mass of the air going into the engine, instead of estimates it, based on what the BMW engineers inserted in the memory tables of the DME.

    I had the exact same situation you described and in my case it was the MAF gone bad. Do NOT buy an ebay cheap MAF, they are worthless (tried three of them -along the way turned into an experiment- and they are all sh*t, believe me; the MAF is too complex to let the Chinese figure it out). You can throw those away in the trash bin. Buy a used original stock Siemens/VDO one, oh, correction, in your case a Bosch one (non Vanos M50 uses Bosch electronics if I'm right).

    Best to eventually install another MAF, but for the time being, weeks, I think no damage will be done. Lots of (race) cars use the Alpha-N system to calculate fuel and timing continuously and have no troubles what so ever. But, if you have changed any of the major parts of the engine/intake/exhaust, then the Alpha-N won't work perfectly fine anymore and will tend to run lean.. It assumes a completely stock M50. If you improve breathing, it will not know that and will a result think less air is going through the engine than what's actually flowing in reality. As a result it will run lean then. Once warmed up, at lower loads, the oxygen sensors will help the DME to adjust, but at full power (and when still cold and oxygen sensors don't work yet), it might cause some damage over time. But as long as the engine runs smooth and fine, I think you're completely safe.
    Last edited by ed323i; 08-08-2018 at 07:25 PM.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  11. #11
    Join Date
    Jan 2002
    Location
    outta SoCal, now CO
    Posts
    1,212
    My Cars
    '98 M3 Alpine White
    If there's anyone who is still working on one of these 6-pin Bosch MAF in a '92 325i M50 or similar, then I'd like to get one voltage reading from a fully operating system.

    There's a Gray/White wire right next to the primary ground (Brown/Orange). With the MAF disconnected and the key ON, I'd like to get a voltage reading on that Gray/White wire. I'm getting 1.8volts on this wire with the wiring diagrams calling this connection a 'common'. There are specs for all the other connections but not for this one.

    Thanks,
    tjm
    See ya later,

    tony
    '98 M3, '92 Dinan3, '05 R1100S BCR, '07 R1200S, Aprilia T

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