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Thread: Running rich on a Stock M3

  1. #1
    Join Date
    Apr 2003
    Location
    CA
    Posts
    2,884
    My Cars
    95 Alpine White ///M3

    Running rich on a Stock M3

    I have a 95 M3 that is running super rich.
    It failed emissions because of High HC and CO content in the exhaust.

    My bumper is black and I can smell fuel whenever I back up and the fumes go to the front of the car....

    I can't figure out why it would be running rich because this car is bone stock.

    I did have a problem with oil in my plug wells, but I put a new valve cover gasket and plug seals in. I stuck the original plugs back in.

    I put some fuel system cleaner in the tank and have been running around for 1 week, but the car still looks like it's running rich.

    any ideas?
    ///M3 Cc#65
    95 M3 Alpine White Acquired 6/17/03
    Cosmos Racing 3.5" CAI / AA Stage II Euro HFM Kit / UUC Stage II Flywheel / M5 Clutch / AA Gen III Exhaust / Bilstein + Eibach Prokit / OEM X-Brace / AA Strut Brace / ZKW + OEM M5 Projectors / Philips 85123 upgrade

    97 Integra LS-Turbo Sold 6/14/03
    10 psi of boost

  2. #2
    Join Date
    Aug 2002
    Location
    Florida
    Posts
    2,853
    My Cars
    M3/4
    Check your o2 sensors to start. Also possible you've got a vacuum leak of some sort that's making her run rich. Bad thing is if this has been going on awhile, you may have drastically shortened the lifetime of the cat..

  3. #3
    Join Date
    Feb 2003
    Location
    Linthicum
    Posts
    504
    My Cars
    99 M3, 00 S2000
    Time for a track pipe...

    Check your injectors out and make sure they're OK and you're not dumping too much gas.

    Check to make sure your O2 sensors are still working properly.

    Check your vacuum lines behind the intake manifold and behind the fuel rail. These are very common to slip off and cause a leak.

    I would think one of these should be your problem, if not, I would do a "check engine light" check and maybe a computer test to see if you get any readings...good luck.
    99 M3 - Stromung Exhaust

  4. #4
    Join Date
    Nov 2002
    Location
    Please god, anywhere but Canada
    Posts
    4,150
    My Cars
    The Bavarian Falcon
    90% certain you have a failing 02 sensor.
    93 325is - total M3 conversion and more - Dinan SC kit - RMS aftercooler and tuning - 395rwhp on 91 octane.
    "....She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself." -Han Solo

    CarDomain page

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