MIL light on every 2 weeks
Hi, I have a 2009 CC sport which I absolutely love. MIL light goes on every 2 weeks with codes P0171 : $07E8 every time. The problem first started last year, when I took it to the dealer, who changed fuel pump, the problem resolved for few days. Since this time I have been using the Shell's highest price gas. MIL showed up again, when I was told there is carbon deposition and asked to use the fuel injector cleaning for 3 full fuel tanks. MIL came back on, this time dealer said, they would have to go in manually and clean up the carbon, which I got it done. Later the MIL came back again in 2 months, since than I have paid a visit to the dealer about 3-4 times with MIL, which comes on for me but they cannot reproduce the same and cannot find any problem with the car.
At this point, MIL comes on once ever 1-2 days with the P0171 : $07E8 code, car runs fine. MIL clears by next day. Please suggest what could be the problem, do I need to worry about this?