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