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Thread: '93 325i Euro O2 Sensor doubt

  1. #1
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    '93 325i Euro O2 Sensor doubt

    Hi everyone,

    I own a 1993 325i E36 (M50B25TU) EUR. I've had a really weird discussion with my mechanic regarding the O2 sensor; He is 100% sure that my car doesn't have an O2 sensor. I've checked RealOEM and there is indeed an Oxygen sensor that applies to my car. I haven't had the time to rise the car and check for myself, but my vote is that the car does have one. What do you think? Is my mechanic wrong?

    Sorry for such silly question. Thanks.

  2. #2
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    Find a new mechanic

    Sent from my VS987 using Tapatalk

  3. #3
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    It's just in an odd spot, so yes your mechanic sucks.

    http://www.realoem.com/bmw/enUS/show...diagId=18_0177
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  4. #4
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    I am already tired of the guy. Thanks for the input guys.

  5. #5
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    Quote Originally Posted by XnWarden View Post
    Find a new mechanic
    Quote Originally Posted by Eric93se View Post
    It's just in an odd spot, so yes your mechanic sucks.
    Guys I lifted the car and couldn't find the O2 sensor. I found a connector you may see in the picture below. I suspect it's the connector to plug the O2 sensor and seems pretty much original to me. What do you think?

    Thanks.

    IMG_5388.jpg
    Last edited by TRF434; 03-15-2018 at 07:34 PM. Reason: Incomplete entry

  6. #6
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    Looks like an auto trans connector.

    Feel for the 02 sensor on the top of the exhaust just before the cats.
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  7. #7
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    Quote Originally Posted by Eric93se View Post
    Looks like an auto trans connector.

    Feel for the 02 sensor on the top of the exhaust just before the cats.
    Look at this picture. It looks that the connector is on the very same spot from the picture on my last thread. I took it from a PelicanParts tech article on the O2 sensor.

    pic7.jpg

  8. #8
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    Quote Originally Posted by TRF434 View Post
    Look at this picture. It looks that the connector is on the very same spot from the picture on my last thread. I took it from a PelicanParts tech article on the O2 sensor.

    pic7.jpg
    Surely looks like the o2 connector to me... what happened to your car?

  9. #9
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    Quote Originally Posted by ultimatetester View Post
    Surely looks like the o2 connector to me... what happened to your car?
    I don't know. The car is a '93 Euro Spec M50B25TU that came to the Latin American market. Maybe BMW decided it was better to chop off the O2 sensor (to reduce costs, maybe?) since at that time there were no emissions regulations in Colombia. The sad part is that I'm in the struggle of troubleshooting a massive fuel consumption problem in addition to an annoying hesitation all the way through the entire RPM range that translates to an extremely low power engine. Even a little Chevrolet Sonic can beat me on the highway easily.

  10. #10
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    Check where the O2 sensor is supposed to be installed in the exhaust pipe to see if there is a plug in the threaded hole. Maybe a previous owner removed it. The car will run without it but not well. Did the car ever run well for you or you got it like this?
    '94 325i Sedan, Arctic Gray: UUC LTW FW, EVO 3 and DSSR, +.020 Maxsil pistons, ASC delete, Eibach shocks/springs, 16" contour reps 238k
    '93 325is Coupe, Schwarz, work beater 299k
    '89 325i Vert, Alpine White: 5spd swapped. Sold
    '04 Toyota Sienna XLE Limited AWD, In progress swapping to M50/G250, http://www.wibimmers.com/board/index...nna-25i-build/
    '05 Volvo V70 R, 6mt, mostly stock, kid hauler 200k Sold
    '85 Toyota LandCruiser: Lifted, gas hog. 205k

  11. #11
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    Quote Originally Posted by jc43089 View Post
    Check where the O2 sensor is supposed to be installed in the exhaust pipe to see if there is a plug in the threaded hole. Maybe a previous owner removed it. The car will run without it but not well. Did the car ever run well for you or you got it like this?
    According to the Bentley manual, 92-95 M50s should have an exhaust system like in the diagram below. However, mine doesn't have that "Y" junction (circled in red) that has the threaded hole where the O2 sensor plugs; each set of three exhaust ports connect directly to a cat converter.

    O2.JPG
    Last edited by TRF434; 03-16-2018 at 12:42 PM. Reason: Grammar fix

  12. #12
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    Does it look stock or like someone has modified it? Also does that plug look like anything was ever plugged into it or is it caked with dirt from being exposed for many years?
    '94 325i Sedan, Arctic Gray: UUC LTW FW, EVO 3 and DSSR, +.020 Maxsil pistons, ASC delete, Eibach shocks/springs, 16" contour reps 238k
    '93 325is Coupe, Schwarz, work beater 299k
    '89 325i Vert, Alpine White: 5spd swapped. Sold
    '04 Toyota Sienna XLE Limited AWD, In progress swapping to M50/G250, http://www.wibimmers.com/board/index...nna-25i-build/
    '05 Volvo V70 R, 6mt, mostly stock, kid hauler 200k Sold
    '85 Toyota LandCruiser: Lifted, gas hog. 205k

  13. #13
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    Quote Originally Posted by jc43089 View Post
    Does it look stock or like someone has modified it? Also does that plug look like anything was ever plugged into it or is it caked with dirt from being exposed for many years?
    It looks 100% stock. I will look at the plug and tell you, but now I believe that nothing has ever been plugged into it, just like my mechanic said.

  14. #14
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    Quote Originally Posted by jc43089 View Post
    Does it look stock or like someone has modified it? Also does that plug look like anything was ever plugged into it or is it caked with dirt from being exposed for many years?
    Ok, here are some pictures of my exhaust system from the exhaust manifold all the way to where the plug should go.
    IMG_5393.jpg
    IMG_5394.jpg
    IMG_5396.jpg
    IMG_5397.jpg

    Finally, here's the O2 sensor plug. It looks brand new. It seems it has always been covered.
    IMG_5398.jpg
    Last edited by TRF434; 03-18-2018 at 03:16 PM. Reason: Missed a picture

  15. #15
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    The o2 sensor does more than emissions and its pretty critical in tuning your air-fuel ratio. I can't imagine the car just not having one

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  16. #16
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    Its obviously been disconnected at some stage - there is still an O2 installed in your exhaust. The 320i I own had its O2 sensor disconnected for a good 1.5yrs before I discovered it was disconnected.
    As mine uses a Siemens ECU as opposed to the Bosch on your 325i, I cannot comment as to how well the vehicle would or would not run with the O2 sensor missing/disconnected. All I can say in my case was there was some hesitation only when the car began to warm up, and 13% higher fuel consumption, but that was about it. The car still ran perfectly fine once warmed up.

    I don't know why something would be installed in your exhaust with wiring but seem disconnected. Can you trace the wiring from the exhaust and see if its just been disconnected at some point?

  17. #17
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    Trf434, I don't see anywhere in your pics the area of where they o2 sensor hole should be. It should be a few inches upstream of the catalytic converters, on the top of the exhaust.
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  18. #18
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    Quote Originally Posted by Eric93se View Post
    Trf434, I don't see anywhere in your pics the area of where they o2 sensor hole should be. It should be a few inches upstream of the catalytic converters, on the top of the exhaust.
    I've realised the first image the OP shared mightn't have been from their particular vehicle... Whoops!

    I recall from my Owner's Manual the mention of Leaded Petrol, and the fact that vehicles sold in some jurisdictions did not have catalytic/emissions control fitted due to the prevalence of leaded fuels. This might be the case for your vehicle, although you'd think RealOEM would make a note of parts specific to vehicles with that option. Might pay to check your VIN and see if there is any mention of emission-control equipment being deleted for your vehicle.

    As for your running rich/very poor acceleration issue, this sounds like the engine is running in a sort of limp mode. Having tried secondhand parts as a cheap means of testing for a bad knock sensor, my vehicle went into limp mode due to a (obviously) bad part.
    The car's acceleration was very poor until 2000rpm, the fuel mixture was exceedingly rich (judging by exhaust odour) and you could tell the injectors were actually batch-firing based on the loud ticking. So you might want to find a mechanic with BMW Diagnostics that can scan the codes on your car and figure out if (a) the DME recognises the missing O2 sensor and (b) other underlying issues that would be causing the poor performance you note.

    A quick note, as well for the OP in particular - European spec. E36s do not have a Check Engine Light, although some (depending on the particular model & DME in use) do have all the wiring present for it; such as your 325i.
    Last edited by B320i; 03-18-2018 at 11:38 PM.

  19. #19
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    That was also for the E32 and E34 that for some country specs there was no cats installed, like for U.K. or Italy versions, the cars came just in version prepared for cat = the cable loom was there.
    I do not have your VIN, but here is for example the ZA version 325i 1993 the exhaust without cat http://www.realoem.com/bmw/enUS/show...diagId=18_0184

    Example E32 750: The car was built 1990-01-17 and is Germany/Austria version. It was ordered in the version CATALYZER PREPARATION CONVENTIONAL EXHAUST TECHNIQUE http://www.realoem.com/bmw/enUS/show...diagId=18_0145 instead of the version with cat http://www.realoem.com/bmw/enUS/part...BMW-750i&mg=18

    As long as the primary sensor =the MAF is reading accurately and there are no vacuum leaks then the engine will run fine - the Lambda sensors are there to make small adjustments for imperfections in the engine - all explained here:
    http://www.meeknet.co.uk/E38/Diagnostics.htm
    Shogun tricks and tips for the E32 series are HERE!

  20. #20
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    Wow, so your car has no cats or oxygen sensor bad for the environment.
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  21. #21
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    quite popular in Europe in those days to order w/o kat when it was not mandatory but just an optional extra, as the non-kat version usually had higher compression, among other things different pistons, see here for example the M30 http://bmwfans.info/parts-catalog/E3...kshaft_pistons
    The E32 735 M30 non kat had 220 HP and the kat version had 211 HP, roughly the higher compression was about +10% , = 10 : 1 compared to 9 : 1, Option 200 = cat delete, version leaded gasoline 200 KATALYSATOR - ENTFALL
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  22. #22
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    Quote Originally Posted by shogun View Post
    That was also for the E32 and E34 that for some country specs there was no cats installed, like for U.K. or Italy versions, the cars came just in version prepared for cat = the cable loom was there.
    I do not have your VIN, but here is for example the ZA version 325i 1993 the exhaust without cat http://www.realoem.com/bmw/enUS/show...diagId=18_0184
    Everything makes sense now. After decoding my VIN and taking into account your input, the car doesn't have an O2 sensor because it was built without catalytic converter:
    VINDecode.JPG
    Also, my fuel cap states that the engine is good for leaded fuel, supporting the fact that the car doesn't have a catalytic converter:
    IMG_5399.jpg
    "Gasoline. Leaded or Unleaded"

    That's strange because in Colombia the use, import/export of leaded fuels was prohibited in 1989, 4 years before the car was manufactured but emissions regulations were non-existent. Maybe BMW had a strong reason to offer the catalytic converter as optional equipment in markets where it wasn't mandatory.


    Quote Originally Posted by B320i View Post
    I've realised the first image the OP shared mightn't have been from their particular vehicle... Whoops!
    As for your running rich/very poor acceleration issue, this sounds like the engine is running in a sort of limp mode. Having tried secondhand parts as a cheap means of testing for a bad knock sensor, my vehicle went into limp mode due to a (obviously) bad part.
    The car's acceleration was very poor until 2000rpm, the fuel mixture was exceedingly rich (judging by exhaust odour) and you could tell the injectors were actually batch-firing based on the loud ticking. So you might want to find a mechanic with BMW Diagnostics that can scan the codes on your car and figure out if (a) the DME recognises the missing O2 sensor and (b) other underlying issues that would be causing the poor performance you note.
    B320i, my problem is very similar to what you experienced. Sometimes acceleration to 3000 RPM is awful. While hitting 2800-3000 RPM one can feel that the engine struggles to get there and then bogs down. While revving up to 4000-4500 RPM it's possible to feel the very same symptom. Struggle and bog. The engine's fuel mixture is without a doubt rich; everytime I park at home, the entire building starts to smell like strong combustion.

    I was to blame the O2 sensor but since my car doesn't have one, I have to discard it as the culprit. I'm thinking of the fuel pump but now I know I should check other components like knock sensors, and cam position sensors. Did you solve your issue by replacing the knock sensors?

    Thanks for the support guys.
    Last edited by TRF434; 03-20-2018 at 03:02 PM. Reason: Spelling fix

  23. #23
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    I used a German VIN decoder, the car was made for Europe and the dummy salapa in your decode is an additional tank filling for export cars = a few liters more that the car could be driven onto the transport ship

    Fahrgestellnummer: WBACB31000FD82972
    Typ-code: CB31
    Typ: 325I (EUR)
    E-F-R-Baureihe: E36 4
    Baureihe: 3
    Bauart: LIM
    Lenkung: LL
    Türen: 4
    Motor: M50
    Hubraum: 2.50
    Leistung: 141 (192 hp)
    Antrieb: HECK
    Getriebe: MECH
    Farbe: 218 - ALPINWEISS 2
    Production date: 1993-07-09
    S199 Entfall Katalysator
    S301 Diebstahlwarnanlage
    S401 Schiebehebedach elektrisch
    S411 Fensterheber elektrisch vorne/hinten
    S415 Sonnenschutzrollo hinten
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    S554 Bordcomputer V mit Fernbedienung
    S657 Radio Bavaria C Reverse III
    S850 Zusätzl. Tankfüllung Export
    S856 Sprachversion spanisch
    S899 optische Signalgebung für DWA
    Shogun tricks and tips for the E32 series are HERE!

  24. #24
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    Quote Originally Posted by TRF434
    I was to blame the O2 sensor but since my car doesn't have one, I have to discard it as the culprit. I'm thinking of the fuel pump but now I know I should check other components like knock sensors, and cam position sensors. Did you solve your issue by replacing the knock sensors?
    Fuel pump won't cause the engine to run a very rich mixture. It may cause stumbling if the engine is experiencing fuel starvation. Found with the engine in "limp," if you try to blip the throttle it may stumble and cough a bit then, too.

    While replacing the knock sensor solved my problem, as I had a bad secondhand part, this may not be the root cause of your problems. Like I said before, you need to find a technician with BMW Diagnostics who can check the DME for stored fault codes. Its a much better thing to do rather than start wasting money on new parts when you don't need 'em
    Last edited by B320i; 03-20-2018 at 07:39 PM.

  25. #25
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    A simple test you can do, pull the vacuum hose from the fuel pressure regulator, if fuel drops come out from the hose, the fuel pressure regulator diaphragm is broken and the FPR cannot regulate the fuel pressure/volume anymore.
    Shogun tricks and tips for the E32 series are HERE!

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