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Thread: E30 diagnostic help - random sputtering

  1. #1
    Join Date
    May 2022
    Location
    Chicago
    Posts
    5
    My Cars
    1991 BMW E30

    E30 diagnostic help - random sputtering

    Hey guys, I have a 91 325i auto transmission - I have an issue that is driving me crazy. Hope you guys can help me out. My check engine light comes on randomly, whether stuck in city traffic or on the highway, smooth or bumpy road, parked or doing 60mph. This can happen for 1 sec or 5 min.

    I can’t find someone that can run a check engine scan and I’ve tried stomp test and cannot get the car to show anything.

    Symptoms: weak throttle response, sputtering, shaking, if at idle it turns off eventually, still shifts but rpm struggles to go up.

    I changed plugs, wires, distributor cap, fuel pump (unrelated), fuel filter, mass air flow sensor.

    Also, On youtube all of the videos said if mass air flow is unplugged, car should turn off. I changed the mass air flow but goes does not turn off. Wondering if I got a faulty part from o’reilleys.

    Please help.

  2. #2
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    Moved to E30 forum
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
    Join Date
    May 2013
    Location
    Tuscaloosa, Alabama
    Posts
    88
    My Cars
    1989 BMW 325i Coupe
    I can yank the plug of my 89 325i and it won't shut off. To be clear, mine has been upgraded to a mass air flow (MAF) sensor and chip. The oem part is an air flow meter (AFM). They are different parts and work differently.

    I would think unplugging an AFM would make the engine shut off, but maybe not. Conversely, the plug from the harness on mine was old and even though it acted like it clicked and locked down, in fact a gentle push with a finger tip would dislodge one side of the plug and that would shut the engine off. In that case, 3 of the pins were still making contact but the 4th, outermost pin on that side was not.
    1989 BMW 325i Coupe
    1989 Suburban 4x4
    2014 Ram 1500 4x4
    1945 Willys MB Jeep
    1959 Triumph TR3A

  4. #4
    Join Date
    Sep 2014
    Location
    KS
    Posts
    1,366
    My Cars
    e24e30e36e39e90
    Could be fuel injectors. I had similar symptoms when I bought the wrong 19lb fuel injectors. Got the right ones and everything was fine. The check engine light would come on when sitting still because the injectors were causing a rich condition that the DME was unable to compensate for. Also good to verify fuel pressures, at rest and while driving.

  5. #5
    Join Date
    May 2013
    Location
    Tuscaloosa, Alabama
    Posts
    88
    My Cars
    1989 BMW 325i Coupe
    Those symptoms also sound like a crank position sensor on its way out. I think that would produce every symptom you have mentioned.
    1989 BMW 325i Coupe
    1989 Suburban 4x4
    2014 Ram 1500 4x4
    1945 Willys MB Jeep
    1959 Triumph TR3A

  6. #6
    Join Date
    Sep 2019
    Location
    Austin, TX
    Posts
    4
    My Cars
    1992 BMW 325iC
    I have an E30 convertible and I have recently experienced the same issue as "thegoatfuel". So what was the culprit and how to fix it? Thanks.

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