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Thread: E90 320i cold start rough idle and stall

  1. #1
    Join Date
    Mar 2017
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    Tasmania, Australia
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    2
    My Cars
    BMW E90 320i

    E90 320i cold start rough idle and stall

    Hi guys, just wondering if you guys could help. I have a 2008 e90 320i and when I start the car cold after it has sat overnight, the idle stumbles and is very rough and once put into gear it will stall. It only happens for about 20 seconds and then it disappears for the rest of the day even after being at work for 9 hours it starts like a dream. I'm at my tether with trying to find out what the issue is. It's not giving any codes. I've cleaned all the intake and sensors and replaced pcv diaphragm as this had a small tear in it and I thought it may be causing a slight vacuum leak. Also cleaned vanos solenoids and changed spark plugs. Any help would be greatly appreciated. Thanks, Aaron
    Last edited by Aaron9364; 03-25-2017 at 01:02 AM.

  2. #2
    Join Date
    Dec 2012
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    North Carolina
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    1,450
    My Cars
    2009 335i M-Sport Coupe
    Rough idle could be coils, injectors, fuel pressure, etc. My first guess would probably be high pressure fuel pump since it's only on start up, after sitting. The best way to proceed would be with diagnostic software, that way you can be sure before buying parts. Even without DTC codes, the software can read out fuel pressure, injector duty cycle, and cylinder smoothness to help you isolate the problem. I can give you links to all kinds of great software if you want.

  3. #3
    Join Date
    Mar 2017
    Location
    Tasmania, Australia
    Posts
    2
    My Cars
    BMW E90 320i
    Those links would be great thank you. I'm wondering whether or not it could be as simple as a fuel filter? Most things I can think of and that you also mentioned should throw a code of some sort I would think. My other thought was of replacing the vanos solenoids, even if they don't fix the problem at least I can eliminate them
    Last edited by Aaron9364; 03-25-2017 at 05:49 AM.

  4. #4
    Join Date
    Dec 2012
    Location
    North Carolina
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    1,450
    My Cars
    2009 335i M-Sport Coupe
    Quote Originally Posted by Aaron9364 View Post
    Those links would be great thank you. I'm wondering whether or not it could be as simple as a fuel filter? Most things I can think of and that you also mentioned should throw a code of some sort I would think. My other thought was of replacing the vanos solenoids, even if they don't fix the problem at least I can eliminate them
    Hey, I sent a PM with software. Fuel filter would usually cause problems at higher load first. You can check fuel pressure with the software to make sure. Lots of times you'll get a plausibility code without an engine light for issues like this. That means the computer thinks there is a problem with a specific component, but it's not sure. ISTA can read codes, read live data, and guide you through test plans to get this figured out.

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