mccullough Posted April 4, 2010 Share Posted April 4, 2010 I fixed my knock sensor problem in my 96 Legacy Wagon 2.2L and my gas mileage did not go back up very much. It was about 21 and is now 23 mpg. I can still smell a slight unburnt gas smell at start up but the engine runs and sounds good. Any ideas? I wonder if the knock sensor on it's way out could cause this. I only have 130,000 miles on it.:-\ Quote Link to comment Share on other sites More sharing options...
NoahDL88 Posted April 4, 2010 Share Posted April 4, 2010 when is the last time you did a complete tune up? How much stuff do you have in the back? bags of sand, bricks and the like. Plugs, wires, air and fuel filter can do wonders. Your O2 sensor may be sluggish. Quote Link to comment Share on other sites More sharing options...
mccullough Posted April 9, 2010 Author Share Posted April 9, 2010 I have not changed the wires but have recently tuned it up w/new air filter, spark plugs, fuel filter and I cleaned the MAF. The car is usually empty w/o alot of junk in the back. I guess I'll replace the spark plug wires and see what happens and then the O2 Sensor if that doesn't work. Thanks much, Dave Quote Link to comment Share on other sites More sharing options...
idosubaru Posted April 9, 2010 Share Posted April 9, 2010 Type of driving makes a huge difference, what have you gotten before and auto or manual? 23 does sound low for average driving conditions. I've seen gas mileage increase 3mpg after a brake job on a vehicle that had perfectly operating brakes, just low pads. When was the last brake job and are you sure they're actually greasing the slides and not just pad-slapping it (common practice)? O2 sensor if it's original would certainly be a place to look. They're not lifetime use parts. Not sure if they're easily testable but it would be only the front O2 that could affect gas mileage. On older generation Subaru's they run perfectly fine with the O2 sensor disconnected. So if you disconnect the O2 (if it's possible on EJ stuff - i've yet to try it) and the gas mileage doesn't change at all (go down) then that might be an indicator that the sensor is bad? In general I figure I'm going to replace the O2 sensor at least once for sure so I do it early and figure I'm maximizing my return on the new part and increased mileage over the life of the vehicle. So I replace them without much thought. There was a recent thread about bad CTS causing engines to run rich, and probably decrease MPG. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted April 9, 2010 Share Posted April 9, 2010 What was the mileage before the trouble that caused it to drop? It's hard to determine what is "bad" without having a baseline to compare to. Quote Link to comment Share on other sites More sharing options...
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