Land Rover '03 DII - Codes P0174, P1174, P0150

All - I have a 2003 LR DII and the SES light came on recently. When hooked up to the computer, it showed the three codes listed above indicating misfire in two cylinders and that the fuel mix was too rich. I have changed the spark plugs, cleaned the O2 sensors, and cleaned the fuel injectors. The light stayed off for about 20 minutes of idling, but as soon as the car was back out on the road, the light came back on again. I also suspect that I may have gotten some bad gas as I currently live overseas - any ideas as to what might be going on and what troubleshooting steps to try next?

None of those three codes are about misfires. Two of them (0174 & 1174) are about running lean, not rich.

The P0150 is basically for a low voltage reading from the bank 2 upstream oxygen sensor. My gut tells me that O2 sensor may just be bad & thus your computer thinks you’re running lean - the other two codes are bank 2 lean codes, and the computer gets fuel/air mix info from the O2 sensors.

However, there might actually be a lean condition in which case the O2 sensor is just doing its job & replacing it won’t do a thing. I’d guess that you either need a good diagnostician with a scantool or you place bets on that O2 sensor, cross your fingers & replace it. If these happen to be expensive sensors, that might be a bad idea.