Started the car just the other day and let it idle until it reached full operating temp. then it threw the code p0174 for lean bank 2. The cars exhaust smelled very rich and the idle was wandering around a bit. I pulled all the plugs on that bank and they were very rich looking. I cleaned the maf, which didn't change anything and made sense since the code was only on one bank. I checked for exhaust leaks and vacuum leaks and found none.

I'm still on the first tank of gas that was in the car after sitting all winter so I thought maybe I could have bad gas. I put in some fuel system cleaner and a little bit of torco to raise octane a little bit. Drove the car today and it runs good doesn't miss sputter or anything. The code hasn't came back yet, but the idle still seems a little off. I'm thinking the oxygen sensor has to be the culprit along with maybe some old gas adding to the problem.

Could a bad oxygen sensor create a problem like this?

 

yes it can