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Thread: very rough idle and stalling issue

  1. #1
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    E30 M3 S50B32 bi-tur

    very rough idle and stalling issue

    Hey all,
    I have a s50b32, it used to drive fine but recently the idle became very rough and the car will stall if i dont give it gas and shakes a lot. Also it became very boggy at the lowend.
    I was hoping it was some cam sensor and I thought it might be the intake cam sensor cause unplugging it didnt make any difference in the car so i changed it and nothing changed.
    So i tested the solenoids resistance and found the exhaust side had an infinity resistance, the wire to the solenoid had broken off so i soldered it back on, the car wasn't bogging down on the low end anymore but the idle is still rough and it still stalls and is shakey and very loud exhaust note.
    I tried testing the solenoids with a 9v battery to see if they'll make an audible click and they do (some more faint than others).
    I also tested the tps and it shows 0.5v at idle and 4.0v at WOT.
    I removed the plugs they seemed fine, brown on the sides and the tip is pretty gray/white.
    I tried to unplug the MAF but it still was lumpy, unplugging it before would run fine using the alpha-n map.

    I'm looking right now to maybe get the carsoft scanner (it's like $40) it says it can read live data and see codes/reset adaptations too.
    Any ideas what the problem might be?
    Thanks

    "Life starts after 6000rpm"

  2. #2
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    EXOTICS
    The Carsoft should provide the diagnostics we need,
    then we can make an educated diagnosis.
    Post back with the results of your scan.

  3. #3
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    MauiM3Mania is offline Observer/Master Skeptic Moderator
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    Did you get this resolved?

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  4. #4
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    1997 BMW M3 S50B32
    Without fault codes and live data you are flying blind. From the sounds of it you are running overly rich, but I wouldn't guess at it. I basically replaced all my sensors on the premise they were 20 yrs old and had tons of heat cycles.
    1997 S50B32, 5MT, 3.64:1 FD, CSL Carbon airbox, KromerKraft headers, VEMS PnP, Schrick 284, Supersprint x pipe & Race Muffler, Rogue shifter, JBR lightweight flywheel, Clutchmasters Kevlar clutch, MCS, Hyper Coils, Ground control plates, Turner bars, Turner camber links, Road Race GT strut bar, PFC pads

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  5. #5
    Join Date
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    E30 M3 S50B32 bi-tur
    I finally received the carsoft yesterday and got it working.

    The initial diagnosis said:
    Error 155 MSS50 Control Module Fault- Fault Memory Master
    Error 19 Aux. Air Pump Relay
    Error 36 Tank Vent Valve

    Then after resetting and driving around for a while i got a new one,
    Error 136 Idle Speed Control Valve
    as well as the above.

    The live data shows the ignition at 22kw and camshaft degree -24kw
    They barely ever move at all +-1 while driving, and the VANOS always says "LATE" i think that's due to it not working well with the euro s50b32 perhaps, i doubt it's not changing at all cause it pulls pretty well in the high rpms.

    The power supply in the live data is all over the place jumping, as well as the TPS even at a steady throttle it jumps up and down between 0.5 and 4.5v
    I'm not sure if those values are right or it's just the carsoft, cause with the car turned off it says 6.2v and i checked the battery and it's 12.4v.
    I had tested the TPS earlier with the car parked, it was working right between 0.5 and 4.5v WOT.

    I wonder if it's some bad ground, i saw a thread in which a guy said that he welded some piece in the exhaust to the transmission and after that it got fixed.

    I'm not sure it's actually the ICV, even though it might be bad, cause even if i give it throttle while parked it still bogs and misfires.

    Even if i remove my foot off the throttle completely while decelerating, it w start stuttering and shaking violently.

    Any ideas? Is the Tank Vent Valve error important? Should i try to reset the adaptations? I kind of dont want to do that in case the carsoft messes the ECU up cause it's not made for it that much. What do you think? Anybody tried already? Thanks
    Last edited by liquidtension; 08-02-2018 at 02:24 PM.

    "Life starts after 6000rpm"

  6. #6
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    Update:

    I've reset the adaptation, the car seems to have improved in general, especially on the low end and feels more torquey and responsive, but it still has the misfirey idle and shaking.

    It runs great anywhere else though. I'm going to check the fuses, i looked over the wiring and the engine grounds they seem ok (next to right ide engine mount to chassis) and upper round 20pin plug to the strut tower (any others i should check?)

    Also i tried the live data from a cold start, the ignition timing starts at 12kw and as the car gets warmer seems to go up to 22
    the Cam timing stays at -24 -25 the whole time

    "Life starts after 6000rpm"

  7. #7
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    Hey guys,
    The car has been fixed! I recently stumbled upon a thread of a guy saying his live data showed the vanos had the exhaust stuck in advance at idle and it caused a rough idle and very loud too.
    He also said it would start stalling when warm, it sounded 100% like my problem. He said that he removed the solenoid and checked it then reinstalled and when he did the car first had a rough idle, then on the 2nd start it magically fixed itself.
    Anyways so i removed the solenoid again, i wanted to check if the pin was hitting the solenoid shell cause it was pretty close before, and it was and i removed the pin and welded it on the other side with the solder joint. After installing it the car started with a better idle at 1000 instead of 600 or so, but the exhaust was still loud. When i started it up again the 2nd time it was perfectly normal with a steady quiet very normal idle.

    Now it's running fine again. I guess that's it, the other guy must have slightly moved the pin from the shell while testing it so it worked for him on reinstallation.
    Hope it helps anyone else.
    Cheers
    Last edited by liquidtension; 08-05-2018 at 09:49 PM.

    "Life starts after 6000rpm"

  8. #8
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    Very interesting,
    glad you found the cause of your troubles,
    only I'm puzzled how the codes don't correspond at all to the fix.

    After the fix-have all codes disappeared?
    Or have you cleared them and they have not reappeared?
    Or you don't know because you have not performed a new scan?

  9. #9
    Join Date
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    97 M3/4/5, 98 M3/2/5
    Curious how you tuned your turbo S50. So you're piggy backing the stock ECU with a megasquirt to run just the injectors?

  10. #10
    Join Date
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    Quote Originally Posted by MIKYZZ4 View Post
    Very interesting,
    glad you found the cause of your troubles,
    only I'm puzzled how the codes don't correspond at all to the fix.

    After the fix-have all codes disappeared?
    Or have you cleared them and they have not reappeared?
    Or you don't know because you have not performed a new scan?
    I haven't rescanned the car again, i dont think the codes would disappear, the tank breather makes sense cause it's a swapped engine, and the 155 code turns out to be a adaptation error or memory error relating to tuning, which makes sense cause my car is chipped and remapped so i guess it's just saying the checksum is wrong or something.

    However, oddly enough the car drove perfectly fine til yesterday when i was approaching a traffic light and it started doing it again!
    I removed the solenoid again, i wasn't so sure it was the pin touching the solenoid shell anymore, anyways i removed the pin even more, and reinstalled, and same thing it ran half ok the first start up, then on the 2nd it was running great again. Pretty odd.

    @tofunin
    Yeah the car isn't actually turbo'd anymore, the turbos started smoking and i removed them many years ago, but yeah i used MS for the injectors and let the ecu control the ignition and vanos.
    Pretty cheap solution back then, however i couldn't really get it to idle well without making it around 11:1 AFR instead of 14ish, my friend with a euro 3.0 followed suite and also put MS and his idled fine with the same settings, must be some mss50 issue maybe changing ignition timing or something. Btw the stock ecu handled some low boost like a champ with no problems giving 12.5:1 afr's WOT for around 3-4months when the adaptation kicked in and it wouldn't let the engine rev more than 5k.

    "Life starts after 6000rpm"

  11. #11
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    First thing I would do is run the Vanos test in DIS.

    This will tell you exactly if both cams operate through their full range of motion. If not, you can be pretty sure that cause most of the misfires and shaky idle.

    If it doesn't pass the vanos test, check the engine timing.
    '98 BMW M3 3.2 SMG Cabrio • Alpinweiß III auf Schwarz • Deutschland-ausführung
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