P0171 running lean

Hi All
Im new to the group and wanted to say Hi first,
The problem I have with my N16 1.5 2004 is that the error code P0171 keeps coming back. If I clear the codes and start the engine the front sensor is switching fine and the rear stay fixed until the cat has warmed up. Once it starts reading it stays pretty low 0.5 to 0.2 V. The car will drive fine but after about 15 minutes the rear sensor starts reading rich and the front starts to lean. It stays like this, the car becomes sluggish and starts drinking fuel ( quarter of a tank to do 30 miles) both sensors read 0.000 v to 0.020 changing .If I unplug the o2 sensors they give a reading around 0.280 V. I have changed both the sensors, checked for leaks and found nothing. It seems strange that it will only fail after 15 minutes roughly even then the warning wont come on it takes awhile whilst it drinks the fuel. Any one got any ideas before I scrape the car? Thanks in advance for any help

Gareth
 
Hi All
Im new to the group and wanted to say Hi first,
The problem I have with my N16 1.5 2004 is that the error code P0171 keeps coming back. If I clear the codes and start the engine the front sensor is switching fine and the rear stay fixed until the cat has warmed up. Once it starts reading it stays pretty low 0.5 to 0.2 V. The car will drive fine but after about 15 minutes the rear sensor starts reading rich and the front starts to lean. It stays like this, the car becomes sluggish and starts drinking fuel ( quarter of a tank to do 30 miles) both sensors read 0.000 v to 0.020 changing .If I unplug the o2 sensors they give a reading around 0.280 V. I have changed both the sensors, checked for leaks and found nothing. It seems strange that it will only fail after 15 minutes roughly even then the warning wont come on it takes awhile whilst it drinks the fuel. Any one got any ideas before I scrape the car? Thanks in advance for any help

Gareth
Hi Gonzo! Could you share with us what was your solution? I experience absolutely the same. Thanks
 
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