Air/Fuel and O2 sensor readings
I have a '99 cali smog 4wd automatic (5spd swapped) that I recently had some error codes thrown due to a failed Air/Fuel sensor (denso 231-9002).
Since replacing the sensor, I have had no issues. Power returned, fuel economy went back up.
Over the past two tanks of fuel I've noticed a sluggishness up hills (hills I have been able to cruise up in 4th gear while maintaining speed/rpm's I now lose rpm's and need to downshift) and decreasing fuel economy. I shot from 11.5ish back right up to just over 17 with mixed driving, the past two tanks wer 16.25 and 15.8 average, driving the same route at the same speeds.
I plugged my obd2 reader back in, and I'm seeing that my new a/f sensor/upstream sensor is showing voltage responses to throttle changes, but once warmed up the downstreak O2 sensor is pegging out at 1.275 volts.
I'm assuming this is the root of my issue? I'm not up to speed on what high voltage means, I'm assuming its telling the ecu that the downstream sensor is seeing an extremely rich condition?
Posted Oct 21, 2020, 3:51 PM UTC
If the sluggishness is really bad, such as flooring it and its just not climbing rpms/seems to hit a wall, it could be a clogged cat.
The downstream O2 is really to confirm emissions and I don't believe it should affect the way the car is running (that's the upstream one). If downstream wasn't working properly, I would expect a code to be thrown, but not really impact drivability.
That's my concern about the cat. When the a/f sensor shit the bed I had to drive it about 60 miles to get back to where I could work on it. I took it easy, but Im really hoping it didnt soot up the cat.