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Thread: E36 323i 1999 m52b25 Misfire and (hissing?) noise when warm

  1. #1
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    Unhappy E36 323i 1999 m52b25 Misfire and (hissing?) noise when warm

    Thank you for reading this and helping me, i really appreciate it Hello my 323 started to have a rough idle, misfire and making a weird sound after i drove it, this happened like the same time it got cold here.
    It was running really bad, misfiring, sounded like it wasn't going on all cyl when i accelerate, but over 3-3.5k rpm it was better (vanos helping?). Here is the video of if, in one video i close the door 2 times which makes the sound louder.
    https://www.youtube.com/watch?v=MPVYNmrIBco
    https://www.youtube.com/watch?v=CR28-ZsF9Qc
    First i checked for leaks with starter fluid - without finding anything.
    Then i got someone to connect it to a computer and then it gave me the following codes;
    https://imgur.com/a/rdTINg1
    DTC
    8 Mass Air Flow Sensor (MAF)
    50 (Connection throttle?) Mechanical fault
    Also abs sensor which i replaced to fix abs light.


    I also replaced the rubber hoose from the MAF, which was bad.
    I got a new MAF sensor and the idle became better, not as rough as before, when i unplug it now it runs noticeable worse, it didn't even react before.
    After doing this i went to check again, this time i got some these following codes;
    https://imgur.com/a/SkXnatI
    8 Mass Air Flow Sensor (MAF) (FROM BEFORE *FIXED*)
    202 - Unknown code
    203 - Unknown code
    68 - Tank valve, electrical fault
    Tried to see what 202 and 203 were and ended up getting this info;
    202 Lambda Regulation Bank 1 Post Cat
    203 Lambda Regulation Bank 2 Post cat
    And these P codes idk about but said (202 and 203) idek if its same but anyway;
    p0202 - injector 2 control circuit (circuit malfunction)
    p0203 - injector 3 control circuit (circuit malfunction)

    and i also found this

    202 Lambda Regulation Bank 1 Post Cat
    203 Lambda Regulation Bank 2 Post Cat
    50 EVAP Control Valve or Response Monitoring Level 2 - related to the first code?? i coudlt really find what DTC 50 means exactly.

    The 68 - Tank valve, electrical fault code COULD be that i disconnected and reconnected a cable which i think is to this before i went to scan, ill upload a picture of it with a red circle around- here --> https://imgur.com/a/OLsNTqU

    Another thing, maybe this has to do with this???? - After changing the faulty abs sensor, the abs light went off but the ASC light blinked and i hear like a rough noise (like its braking) and it wouldnt accelerate AT ALL, and like misfire all the time, like no power, so i pressed the button to deactivate the ASC and it lights up now, not blinking and now i can drive, the only problem is the ABS light gets on whenever i forget to deactivate it and it will sound weird.
    Last edited by reeeee; 12-11-2018 at 04:39 PM.

  2. #2
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    Seems like several things are going on. The first thing you checked for, vacuum leaks, is the most common cause for this kind of trouble. Perhaps you should check/replace the part below the intake manifold that recycles oil fumes (forgot its name). That's also a common cause of vacuum leaks and other trouble.

    Important question: Did you buy a Siemens or VDO MAF, because if you buy a Chinese or no-name one from Ebay, it won't work and you'll continue to have problems (I know, have tried three different ones and they all sucked big time).

    If everything else is working fine, the engine (if not tuned with other intake manifold or camshaft) should run perfectly fine without MAF (and I mean perfectly fine, you almost shouldn't be able to tell the difference; driving away from idle it's a bit less smooth, but that's it more or less; it should develop full power).. So, if it doesn't then something else is off.

    What helps a lot in these cases is connecting a laptop with INPA software, so you can see all live sensor values. Then you can easily tell if for example a coolant temp sensor or intake air temp sensor is off. Or if the oxygen sensors are performing as they should, or if the DME is asking the injectors to inject way more or less fuel than one would predict. Helps a lot in diagnosing cases like this.

    If the 202/203 codes indeed are the post-cat oxygen sensors, then those should have no influence at all at how the engine runs. As a matter of fact, you have a European 323i and it doesn't have post-cat oxygen sensors (unless Sweden has different regulations than the rest of Europe).

    P.S. Update: Just reread your post, and the hissing noise quite certainly points to a vacuum leak, so you have to check all rubber hoses below the intake manifold. One hose between the fuel pressure regulator and the intake manifold. The circular oil fume recycling unit below the manifold, and all hoses and rubbers (to head, vanos side, rubber to intake manifold, hose to oil dip stick). And the hose that goes to the fuel fumes recycling unit/valve. And the rubbers and hoses to the idle control valve... Quite some rubber below there, and all of them quite difficult to get to.
    Last edited by ed323i; 12-11-2018 at 05:41 PM.


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

  3. #3
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    Thank you for your answer ed323i, Much appreciated. The MAF I bought was a new one from Germany (Autodoc) with brand STARK. It has 3 years guarantee, and what I read online if you have a working MAF engine will react when removed, the one I had before didn’t make a single thing difference. The idle is better with this one, so I assume it works.

    The noise only hears when hot and the hotter the engine is the louder noise, when I close door which changes the RPM, the sound becomes louder as you may hear. I will get someone to close the door while I’m listening from where it can be tomorrow.

    The sound comes from in front of engine, under manifold front ish, I don’t know the name but like the cylinder shaped thing left of the oil filter. I sprayed starter fluid pretty much on every hoose I could see and some under intake but didn’t notice anything. But I will take a look at the ones under the Intake and the other hidden ones.

    So these codes can basically just be because of a leak? And the codes basically telling me engine runs bad?

  4. #4
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    The problem is I'm not used to reading numerical codes (202, 203 like you posted). I use INPA and it always shows a description of what is really going on.
    On several sites 202 and 203 are listed as post-cat oxygen sensor.. But in your case that can't be possible because your car has no post-cat sensors.
    On another site I found that 202 and 203 are related to "202: Lambda regulating limit Bank1 and 203: Lambda regulating limit Bank2".. So, that makes more sense.

    You'll get that error if you have a very big vacuum leak, after the MAF, which causes the DME to think a lower than real mass of air is entering the engine. The hissing noise you hear is very probably air that also enters the intake manifold, without it being measured by the MAF. So that messes up all DME fuel injection calculations. The higher the revs and power, the less influence the vacuum leak has. At idle the vacuum is very high and at wide open throttle (WOT) the vacuum is zero (pressure in the intake manifold equals pressure outside).

    So, I think you should continue looking for vacuum leaks. You could perhaps connect a vacuum cleaner to the rubber boot in front of the intake manifold and make some sort of seal. Then you can hear where air sucked into the manifold and fix it. Or you could go to a garage that has a smoke machine for this purpose. Then smoke will come out of the leak.

    I'm not sure about the STARK MAF. My experience with anything other than Siemens/VDO has been really bad. On the other had Stark is German brand. My engine now runs on 6 Stark coils and they seem to keep on working just fine. A MAF is a lot more complex product though, so time will tell. Once you've fixed the vacuum leaks you can try and run without MAF. If it runs as good as with the MAF, then the MAF is probably fine. If it runs better than with MAF, then you might want to try a used Siemens MAF (new they are very expensive).

    Good luck!

    P.S. If there was no hissing noise, then your problem could also be caused by a bad fuel pressure regulator, or perhaps a very bad pre-cat oxygen sensor.. But now I'm 99% sure it's a common vacuum leak.
    Last edited by ed323i; 12-11-2018 at 07:40 PM.


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

  5. #5
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    So when the engine is hot the hoose will expand making the leak bigger? That’s why it dont misfire when cold?
    I also found this under the intake, is this supposed to look like this? Looks like a cable should sit there. https://imgur.com/a/q3usWcK

  6. #6
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    Last edited by reeeee; 12-12-2018 at 09:48 AM.

  7. #7
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    Most probable cause is the hose that goes from the head (Vanos area, like shown in the photo) to the oil vapor recycling unit below the intake manifold. You can unclick that hose by pressing the tabs on it and then pulling it off. Then inspect it thoroughly.. It only costs like 10 euro to replace.

    Other photos show a bit of sweating, but nothing serious, it seems. You could try to retorque the oil bolt (for the Vanos) a bit and that might stop the sweating. Or perhaps loosen it and then fasten it again, using a torque wrench, applying the official amount of torque (look it up in some BMW repair manual, like the Bentley manual, or perhaps the online TIS website).


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

  8. #8
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    Is this the hoose that i can uclick and inspect? https://imgur.com/a/wNjcIFb
    Sorry, I’m not that good on different names.

  9. #9
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    or do you mean this one in blue? https://imgur.com/a/XXknfTy

  10. #10
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    Yes, the one in blue. The oil fumes from the engine/head go through that hose. They get sucked out with the intake manifold vacuum, then the oil collects in the cylindrical part below the manifold and then the oil is dumped back in the block through the hose to the oil dip stick.

    The other one (the red one) is a pressurized oil hose for the Vanos. It seems to leak a little, so that's the one where you can fasten the bolt a little, to hopefully stop the small leak.


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

  11. #11
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    **UPDATE**
    I took out this hoose today and inspected it, aswell as testing it with compressed air without seeing any leak. Here is a picture of the hose;
    imgur.com/a/C9QQHYO

    I didnt notice any other hoose that was bad aswell, from what i saw.

    I checked all coils to see any cracks or oil at the bottom of them but they all was dry and fine except this one
    imgur.com/a/BdYlPf4
    which has looked like that since summer and it has gone good - no trouble with it looking like that.-
    I then checked the spark plug area for oil, most was dry and fine but noticed a very small amount of oil, Pic;
    imgur.com/a/pWg8xpJ
    imgur.com/a/XcGgOLw
    imgur.com/a/7fxeKeI

    But since none of the coils had oil on them i guess its nothing to worry about.

    The weird part;
    I haven't been hearing the hissing noise since 1 day now, and i drove it pretty hard today after inspecting so it would get hot, but the hissing sound wasn't there, atleast not as loud - i cant remember hearing anything.Maybe it will come back after i have been driving it for a longer bit? idk

    **BUT** The misfiring is still as bad, when i hard accelerate is misfires. It still has bad idle also.
    I'll upload a video of how it sounds when i accelerate on high gear so it will misfire. Here's the video: https://youtu.be/ZD2e5m11CkI
    Last edited by reeeee; 12-13-2018 at 07:45 PM.

  12. #12
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    It could also be the valve cover gasket that's leaking, probably in the area near the Vanos where you heard the hissing noise.

    If it's badly misfiring also on high loads and higher rpms then it could also be the crankshaft position sensor or the camshaft position sensor.
    If you floor it, there is no vacuum in the intake manifold and vacuum leaks shouldn't have such a big influence anymore.
    Vacuum leaks give the most symptoms at low loads, when the throttle butterfly valve is mostly closed and as a result a high vacuum exists in the intake manifold.

    I think you can disconnect the camshaft position sensor and see how it runs then. The DME should understand this and fall back to running the car in wasted-spark mode using only the crankshaft sensor. If it runs a lot better, then the camshaft position sensor is the probable cause.

    The crankshaft position sensor is a bit more difficult to diagnose.

    If you could find someone who has a laptop with iNPA and the OBD-USB cable, that would help a LOT diagnosing your problem. Looking at the live values will make a lot clear.
    Perhaps there are local BMW clubs in the area that can test it for you for a low price, like 15-20 euro's or something. Or you could go to a BMW specialized garage and have them look at the INPA live values.


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

  13. #13
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    Small little update, i removed the dipstick while engine is running and held a paper piece above it, it wanted to suck it in. So pcv fine.
    Removed oil cap, also gets slightly sucked in.

    I saw this: imgur.com/a/aqvF84z around the intake, looks like intake manifold gasket? the red thing.
    Here's a close up pic: imgur.com/a/vxjsGMJ

    I think it looks like it, like this part; imgur.com/a/s8OjlLz.

    I sprayed starter fluid around it but didnt notice anything.

    - - - Updated - - -

    And hissing noise still gone, pretty weird. But its till misfiring as usual, and bad idle.

    As you can hear in this video; https://youtu.be/ZD2e5m11CkI
    Last edited by reeeee; 12-16-2018 at 05:53 PM.

  14. #14
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    May not be an issue but
    The check engine light doesn’t show when ignition is on, and I tried several obd2 scanners with adapter from my 20pin and none could connect to ECU, is this a sign of broken fuse to computer?
    Might not be anything but just saying.

  15. #15
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    European E36's don't have OBD2, so modern OBD2 scanners can't connect. You can use INPA thought with a Windows laptop, OBD-to-USB adapter and 20-pin-to-OBD adapter. It's really great and will help you diagnose your problem and any future problems.

    European E36's also don't have check engine light, so also no problem there.

    Photo's and video's alas don't help me diagnose the problem.. I think INPA would be the best next step for now. There is a great thread on how to install INPA on the Z3 forum. Here it is: https://www.bimmerforums.com/forum/s...xperimentation .
    Last edited by ed323i; 12-16-2018 at 07:15 PM.


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

  16. #16
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    Thank you a lot Ed. I found this cable which I can buy and get this week https://imgur.com/a/Oj3SeOn

    But isn’t this the manifold gasket u think?
    https://m.imgur.com/a/aqvF84z
    Last edited by reeeee; 12-17-2018 at 03:24 AM.

  17. #17
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    Had a second look at the manifold gasket photo, and I think you might be right.. If it's damaged, then you would expect it to be a vacuum leak. On the other hand, if spraying starter fluid there has no influence at all, then it seems like it's mostly sealed.

    The USB cable seems fine. Just make sure it has the FTDI FT232RL chipset and not the CH340 or any other chipset, because then you'll have a lot of disconnects and other problems (useless). Price seems okay (21 euro I calculated) as it's local. You can get it cheaper at ebay, but you'll have to wait almost a month before (if) you get it.


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

  18. #18
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    Awesome i ordered this morning i will take another look and pray some more in that area just to be sure.

  19. #19
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    Update on the intake manifold gasket bit that I saw, my friend with a e36 it looks the same and it runs fine. So can’t be that.

  20. #20
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    That piece of red rubber is normal, its a tail piece of the intake gasket, that's just the way they are. The sweating of oil on the vanos oil line is also very normal, it's not the banjo fitting that sweats it's the crimped connections of the rubber that leaks a bit, and what I see there is super minimal so there is no need to replace that hose. I would not recommend to tell people to tighten that banjo fitting because they can strip it if they aren't careful.

    I would recommend a new valve cover gasket and new grommet seals, be sure to read DIY guides if you do it yourself. Don't buy victor reinz or the other cheap brands, go with OEM BMW or Felpro. Also you are probably due for a new set of ignition coils, they come with the rubber bottoms. Over time they will leak high voltage and what your experiencing sounds like they are shorting and your loosing power when accelerating.

    This seller will ship to sweden if you don't have a good price locally.

    https://www.ebay.com/itm/Pack-6-Igni...4/254021574748
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
    Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".

  21. #21
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    Oh ok good to know. Thanks, but will bad coils cause pending idle and misfiring only when hot? I was thinking it would be misfiring all the time if so

  22. #22
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    I had intermittent misfires due to coils, could trigger it by flooring it. Can't recall if it had anything to do with temp.

  23. #23
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    Its not just misfiring when i floor it, it misfires basically all the time its warm and i accelerate normally, if i do it really slow it wont misfire (as bad atleast), sounds like a boat when it happens. (DOESNT MISFIRE OVER 4K RPM)
    The idle is pending, worse when hot
    Also smells like shit from exhaust.

    I will probably get the cable tomorrow then i can connect it to inpa...
    Last edited by reeeee; 12-19-2018 at 07:42 AM.

  24. #24
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    Based on what you describe, I think the DME is having a serious problem determining/calculating the right amount of fuel to inject, and it's often injecting insufficient fool, causing a very lean mixture, and subsequent misfiring. For this to happen, there has to be a major vacuum leak or a major problem with one of the important sensors the DME uses to calculation injection times (MAF sensor, coolant sensor, oxygen sensors).

    Nice thing about having the cable and INPA, is that you'll know what exact BMW error codes are stored in the DME, as the ones you showed in your first post aren't clear enough.

    Perhaps, until you have the cable, you can you retest again with the MAF disconnected, in all rev- and load-ranges and see if you get the same amount of misfiring and all? (yeah, I'm still not very confident the Stark MAF is perfectly calibrated like the Siemens ones).

    You can also try to run without the oxygen sensors connected. Remove the beauty cover on the driver side of the engine (the one that covers the fuel rail), and then disconnected both O2 sensor leads and then have another run and see what happens.

    Now I think of it, could also be a fuel related issue, of too low fuel pressure due to bad fuel pressure regulator, or fuel pump. The fact that it runs fine over 4k rpm and high loads seems that contradict that though.

    Hmm, perhaps best to wait until you get INPA running.. Then make a movie or screenshots where you record all live values, and write down the error codes.. I think we'll be able to find the cause a lot sooner then.
    Last edited by ed323i; 12-19-2018 at 02:58 PM.


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

  25. #25
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    Yeah im pretty sure ill get it tomorrow, then i'll setup inpa and all. Maybe theres another way i can contact you Ed? Like for faster messaging with pics and stuff, and thanks alot.

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