Trying to diagnose reduced fuel mileage and O2 sensor data
I am experiencing reduced fuel mileage, but no other apparent symptoms or codes set. The car seems to run fine, as usual, but with noticeably increased fuel consumption by about 10-12 %. I don't think this is due to weather, winter fuel, etc.
In my exploration of this, I have graphed, using VIDA, oxygen sensor, short and long term fuel trim data, and engine RPM, see the attached graph.
Something I notice, and do not understand, is that the post-cat O2 sensor varies pretty much all the time. My understanding of this function is that this output voltage should remain fairly constant under reasonably constant load conditions, at a voltage about .7V, indicating an oxygen rich condition on the outlet of the catalytic converter. This does not appear to be the case.
The red trace data peaks are the result of lightly blipping the throttle.
Ideas?
PDX-Vancouver, USA
2005 XC70 140,000
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