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  1. #1
    Registered Member
    Braeside , , Australia
    Member No: 184063 petertaylor is an unknown quantity at this point petertaylor's Avatar
    Join Date
    Nov 2010
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    BMW 540i flat spot

    I am hoping someone has some ideas coz i'm stuck ! My 540i is E39 2001 mod. It idles fine and runs fine but under load such as going up a hill it suffers what feels like a lean off at 3500 . It suffers through this until about 4200 then runs clean through to redline (6100)
    I have replaced then checked the air mass meter , I have replaced the 2 pre cat oxy sensors, on the BMW scan tool it shows no codes , I have had the Vanos unit checked and all is good ,I have had two seperate specialists look for vacuum leaks one using the "smoke machine"Plugs are new and correct heat range but I get this flat spot between 3500 and 4200 under load.
    I have just bought a new fuel filter /accumulator and also the fuel vent valve which will get replaced Friday , but if this does not work I am at my wits end! Hopefully someone else has met this issue and can help !!

  2. #2
    User Level 8
    San Jose, CA, United States
    Member No: 21320 edjack will become famous soon enough edjack's Avatar
    Join Date
    Dec 2001
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    Yes | No

    The pressure regulator is part of the fuel filter>

    that might very well fix it.

    The other thing would be to get the BMW tool that allows you to patch into the fuel line, and observe the pressure when this occurs.
    Ed in San Jose. BMW CCA member since 1987 (Nr. 62319). Golden Gate Chapter. '97 540i 6 speed. Build Date 3/97. Aspensilber over Aubergine leather.

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