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Excessive fuel use, fuel smell after journey, no fault codes, -ve trims

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here Excessive fuel use, fuel smell after journey, no fault codes, -ve trims

This topic contains 2 replies, has 2 voices, and was last updated by Mark Appleton Mark Appleton 3 months ago.

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  • #990299
    Mark Appleton
    Mark Appleton
    Participant

    My 2001 325i uses more fuel than indicated by the trip computer and smells of fuel after a journey, but presents no fault codes, though the long-term trim is negative on both banks (straight-6 engine). There are never fuel puddles or drips under the car. Also, I can hear the fuel pump squealing when I get to 2500 rpm, or so.

    I looked underneath at the fuel filter and noted a broken vacuum elbow to the fuel pressure regulator built into the filter – could the pump be over-pressuring as a result? The filter itself is very old (30,000+ miles), but I don’t know how long the vacuum elbow has been broken. I am replacing the filter/reg later today.

    In case this does not fix the issue, should I check for leaking injectors/seals?

    Cheers,

    M.

    • This topic was modified 3 months, 1 week ago by Mark Appleton Mark Appleton.
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  • #990318
    Casey C
    Casey C
    Participant

    The first part made me think o2 sensor, purely based on reading about symptoms of a bad o2 sensor if it’s running rich. Of course, I’m basically a novice so keep that in mind. Also don’t know much about BMW, but on a Honda when I replaced the upstream o2 sensor (no code) it seemed to improve the fuel economy (which had been pretty poor for a while). Hopefully it’s the vac elbow / fuel filter issue only.

    #990399
    Mark Appleton
    Mark Appleton
    Participant

    I replaced the filter and elbow and the car no longer smells of fuel after a journey, but the trims have skewed toward positive. I’m told that this is to be expected while the ECU adjusts to the new setup.

    I found a full set of pre and post-cat sensors for £35, so I might just change them all – the car has done 82,000 miles, and while 100,000 is the common interval, I’ve already got the tool.

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