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Re: MPG dropped from 27 to 18 Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Thu, 1 Mar 2007 12:15:45 In Reply to: MPG dropped from 27 to 18, Porter McManus, Thu, 1 Mar 2007 11:49:28 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Saw your note over on the General board, too.
It's unlikely to be the O2 sensor. I assume you aren't getting a Cehck Engine Light. The trip level for faults associated with emissions (like O2 sensor) are pretty sensitive in an OBDII car as your '97 is, so a bad O2 sensor would light up the CEL right away.
So, let's assume you don't have the CEL on. Let's also assume that you haven't been driving the car harder - the biggest change to mileage is the device that pushes the gas pedal (the driver). Even minor driving habit changes can make big mileage changes.
I would guess that the lack of backpressure from the airfilter is messing with the Manifold Pressure sensor (MAP). The MAP, along with engine speed and intake air temperature is how the engine control determines how much air is going in, and how much fuel to add. A lower-restriction filter shouldn't make much of a difference, but that could be it.
If the CEL is off, and everything else looks OK, I'd try switching back to the old filter. If the gas mileage goes back up, then I'd say the lower restriction filter is messing with the MAP, and the engine control is commanding more fuel.
posted by 192.249....
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