Surging idle, engine stumbles during acceleration.

[LeakySeals]

2005 Chevy Malibu Classic. 2.2 ecotec. 125k. Sudden surging idle and stumbling engine. Scan of ODBII reveals no codes, all monitors ready. There are GM OEM enhanced codes though. P1137, P1171. Problems with the bank 2 O2 sensor. Which is behind the catalytic converter. Could a rear O2 sensor actually be the cause of the idle problems? I thought all they did was monitor emissions. Or are there two different problems? Attached are some photos including live data.

 

[1 SX]

When my bank 2 O2 sensor became "lazy" on the Elantra it did not really affect the idle, nor did it throw a check engine light with my driving, (but did under previous owner) Gas mileage took a hit, and throttle response was also affected, requiring more throttle for acceleration, and initial "tip in" was soft. Not too sure on chevy though, could be much different.

 

[Lubener]

I would check fuel pressure and for vacuum leaks.

 

[spasm3]

Check for a vacuum , intake air leak.