Re: 940 Turbo Gas Mileage - Air Cleaner Case
"thunderbeast" <firstname.lastname@example.org> wrote in message
> 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
> no adjustments - If there was a vacuum leak, the CHECK ENGINE light would
> 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
> 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
> 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
> 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
> through to see if there is an appreciable difference.
> Am I dreaming or does this make sense?
> Dave in Oregon
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