Re: Possible problems related to Code P0171
Crappy gas milage and the code P0171 sounds as a problem with O2 sensor.
I would not expect problems with the gas or fuel filter, otherwise the other bank should have the same problem. Does the exhaust smell raw gas, which would be an indication of too much fuel. Eventhough you got a fuel mixture too lean message, if the O2 sensor is faulty it could measure a lean mixture, while it is rich. Would explain the rough idle and higher then normal fuel consumption.
Do you have a scanner which shows live data? If not, and you have an Android phone, you could get the free app named Torque. You then only need a bluetooth dongle, which fits in the OBDII port and makes the connection between the android and the jeep.
You can then check the O2 sensor voltage. There are 4 O2 sensors, 2 upstream sensors (upstream of the mini cats) and 2 downstream sensors (so downstream of the mini cats). The upstream sensors are directly related to the fuel injection finetuning, while the downstreams are more for the mini cat performance.
Bank 1 upstream sensor is shown as 1-1, while the bank 2 upstream sensor is shown as 2-1 (the downstream sensors are the 1-2 and 2-2).
The voltage of the O2 sensor should go up and down in between 0.2V and 0.8 V and should do this change very often. If the reading is fixed or jumping a bit only, the O2 sensor needs to be changed.
Further to this, if the previous seems to be ok, you could check the fuel trim values calculated by the PCM.
These figures are shown as STFT and LTFT, which stands for Short Term Fuel Trim and Long Term Fuel Trim.
The STFT is the actual fuel trim , while the LTFT is an average over a longer period.
Let us know what you find.