Hi Guys,
I have a 2002 ford focus st170. It's throwing up code p1131 Lack of Upstream Heated Oxygen Sensor Indicates Lean - Bank No 1. I am getting loss of power, rough idling and poor fuel economy. After some research I cleaned the maf, plugs and checked for air leaks, but couldn't find any. The car is running slightly better but the cel came back on again with p1131. The lamda that it refers to was replaced last year then the car was stood for 11 months as i was away, so I can't see it being a bad sensor. Any ideas anyone?

Andy