940 Turbo Gas Mileage - Air Cleaner Case

Discussion in 'Volvo 940' started by thunderbeast, Aug 24, 2005.

  1. thunderbeast

    thunderbeast Guest

    I wrote several months ago about the miserable gas mileage I get from my
    1994 940T (automatic) Wagon. I still get about 14-16 Miles per Gallon in
    the city and up to 22 MPG on the highway. This is far below expectations,
    and feedback from the group suggested that something was amiss - probably
    vacuum or turbo hose. The Volvo specialist that has worked on the car for
    years shrugged his shoulders and told me that "it is what it is - There are
    no adjustments - If there was a vacuum leak, the CHECK ENGINE light would be
    on.

    The Volvo dealer told me to go find the highest price premium gasoline I
    could buy and use it. Premium gas did get me about 2 MPG, but it still
    seemed way too low.

    Tonight I discovered that the plastic case that holds the air filter has not
    been properly closing. A previous owner (or mechanic) had broken off the
    clamps that hold the two pieces together. Instead of the clamps, sheet
    metal screws were used to hold the two pieces together at the four corners.
    One of the screws had stripped out of the plastic below, and the tension
    from the air filter gasket had opened a seam between the two pieces letting
    in large volumes of outside air.

    My new theory is that this outside air is not welcome, and that the O2
    sensor is getting a false reading - telling the fuel injection system to
    keep adding gas to the "lean" air mixture it sees created by the breach.

    I have re-sealed the box (using a new screw) and will now run a tank of gas
    through to see if there is an appreciable difference.

    Am I dreaming or does this make sense?

    Dave in Oregon
     
    thunderbeast, Aug 24, 2005
    #1
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  2. thunderbeast

    James Sweet Guest

    The airflow sensor is after the airbox so the leak shouldn't effect fuel
    economy, it's certainly not good for the engine to be breathing in all that
    unfiltered air though.

    How's the tire pressure? That can make a big difference, it's also worth
    checking the plugs, cap, rotor, wires, and timing. I would expect closer to
    25 mpg on the highway, I find the best fuel economy comes with midgrade
    fuel, premium gives just a tad more pep in hot weather but slightly lower
    economy.
     
    James Sweet, Aug 24, 2005
    #2
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  3. thunderbeast

    David Kaplan Guest

    Just got it back from my regular mechanic. He agrees with the other
    mechanics: It is what it is. Having checked out the vacuum lines, O2
    sesnor, and computer diagnostics, he could offer no further help.


    Too bad! I thought I had a nice car that could be the family campmobile and
    get decent gas mileage. It just seems odd that a four cyl 2 litre automobile
    uses 40% more gas than a full-sized chrysler minivan with a 3.3 litre engine
    (I used to get 28 mpg at 80 miles per hour in the old Grand Caravan that I
    replaced). To me, however, if the Volvo wagon gets the same mileage as a
    HUMVEE, I may as well have the room. I didn't buy it for speed, but I guess
    that is how it was optimized at design.

    I am terribly dissapointed. I am just happy that I didn't invest $35K for a
    new one.

    THIS PIG IS FOR SALE!

    Dave

    This car is going on the market
     
    David Kaplan, Aug 24, 2005
    #3
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