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Thread: Help !!! Fuel Tank Breath.valve failed symptoms

  1. #1
    Join Date
    Nov 2004
    Uganda, East Africa

    Default Help !!! Fuel Tank Breath.valve failed symptoms

    Hello, E34 1990 M20 525IA Japan spec. I have poor/rough Idle after starting the car, mostly it will go off right away if I don't step on the accelarator. Will have to step on it for like 10 mins to start holding idle, afterwards it will keep reving up and down between rpm 1000 and 1500 until engine is warm enough, this now leaves me with abad take off until rev goes above 2000rpm, the car goes baa baa baa baa......until rpm hits 2000, anthing above this, car runs very smooth.

    If I disconnect the power connector to the Fuel tank breather valve, cold startup is good and will hold the idling, however when engine is warm it will behave same way its does when Fuel tank breather valve power connector is on, but alittle better, and leaves me with the rough takeoff.

    Any Ideas...... guys. right now its now easy to procure new parts in ma country, is there a quick fix? besides am I harming anything If I run car with Fuel tank breather valve connect off?


    NB. tommorow is a holiday in ma country, I may not respond till friday.

  2. #2
    Join Date
    Jul 2005


    I am not sure if this is the solution, but I had a similar problem with my 90 mod. 525i. On idle it would sometimes rev up and down between 1500-2000 rpm. The solution for me was that I disconnected the idle valve from its hoses(not sure if that is the correct name, english is not my native language)and sprayed some silicone lubricate into the valve.

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