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Thread: 330ci Long Crank When Cold/rough idle

  1. #1
    Join Date
    Jun 2019
    Location
    Wall New Jersey
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    3
    My Cars
    2005 Bmw 330ci convertib

    330ci Long Crank When Cold/rough idle

    Hello! I am new to e46 ownership and have been a little puzzled by what has been going on with my car, however it is not a new issue with me, it has been occurring ever since I bought the car. It seems to crank very long only on cold starts.

    Early mornings after the car has been sitting overnight or even outside for periods of time it will crank for a long time, and when it finally turns over, idles roughly for a couple of seconds. It is only the initial startup though which is rough, as after I'll turn it on and turn it off again, it will startup fine. The rough idle like I said only lasts a few seconds, but tapping the gas will cause the car to idle smoothly and at a more reasonable rpm. The car drives perfectly and does not seem to have any performance issues.

    I sent the video to my mechanic and he originally said it could be a weak or dying fuel pump. While this could be true I have tried to turn the key to position 2 and hold sit there for a minute, (priming the fuel pump) but that seems to have no effect. I can still hear the pump priming as well.

    It was then suggested by a different mechanic that it could be a draw in the battery. The car once sat for about a week though, and it started up beautifully, so I can pretty much rule that out.

    Does anybody have any ideas what this could be? I have searched the forums many times and the closest thing I could find was a bad MAF, and my car has a brand new one on there now. Thanks!

  2. #2
    Join Date
    Jul 2011
    Location
    Arlington, VA
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    9,933
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    2018 BMW M240i
    The first step in diagnosing a problem is to scan the engine computer (DME in BMWspeak) for codes. The engine trouble light is on only when an emissions related code is present. It does sound like the fuel pump is going bad. Did you get maintenance records when you bought the car? The pump is good for about 5000 hours so mileage may not be the best indicator of the pump’s remaining life. Also, when was the fuel filter last replaced? The fuel filter contains the fuel pressure regulator. The fuel pressure has to be at least 50psi at all engine speeds and loads. Item #2 in the link is the cap for the fuel pressure test valve.

    https://www.realoem.com/bmw/enUS/sho...diagId=13_0900

  3. #3
    Join Date
    Jun 2019
    Location
    Wall New Jersey
    Posts
    3
    My Cars
    2005 Bmw 330ci convertib
    I have Creator c310 scan tool and no codes are present. The car does have few service records however the fuel pump and fuel filter were not replaced as far as i know.

  4. #4
    Join Date
    Jan 2015
    Location
    Timaru, New Zealand
    Posts
    1,132
    My Cars
    Two Z3 Roadsters
    With a warm idling engine, check your short term fuel trims. IF they are >8% then you likely have a vacuum leak. rev the car for 20 -30 seconds. If the trims reduce, its confirmed that you have a vacuum leak.
    1999 2.8L Z3 Roadster,
    2000 3.0L Z3 Roadster,

    There is only one thing more pleasurable than working on a Z3, that's driving it top down on a fine day.

  5. #5
    Join Date
    Jun 2019
    Location
    Wall New Jersey
    Posts
    3
    My Cars
    2005 Bmw 330ci convertib
    Thanks to both of you guys I appreciate the help. I found a video on youtube which seems like it could be right up my alley and does not seem hard to diagnose. https://www.youtube.com/watch?v=6ezt4M1NZDk.

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