Ok, help time... my fuel mileage is taking a s*** on me.
Could it be:
-O2 sensor(s) starting to fail? I'm getting a voltage reading that peaks around .8V on what I think is the upstream sensor, but drops down to .1V regularly. It doesn't hold at either. What I think is the downstream sensor seems to hold pretty steady at .7V, but occasionally dips down to .1V. I monitor it on the Torque App.
-A crappy winter fuel blend from the gas station mixed with frigid temps? I haven't really had a problem until the past month or so since the temps have been dropping.
-Catalytic converter getting clogged? There is no hesitation when accelerating from a stop, but when giving her some gas on the highway, she hesitates for a split second after she downshifts into 3rd gear.
There are no idle issues, but seems to make a little bump noise on cold startups. Nothing that sounds wrong, just a bigger burst of fuel maybe? I don't smell any fuel that would lead me to believe there is a leak anywhere (had that problem with my old Protege), but I do think she's burning a little rich due to the soot on the exhaust. Lack of sensors at to the OBDII port don't allow me to monitor fuel flow or pressure or A/F ratios (as I'm sure many of you know).
I'm baffled now... HELP!?!?!?