P0136, already replaced O2 sensor

Question

I keep popping a p0136 code. When engine light first came on I got 4 codes, p0136, p2771, p2770, and p0436. I replaced the solenoid purge valve and bank 1 sensor 2 heated oxygen sensor. I have an 09 Kia Rio and after part replacement I got the p0136 code again. I swapped out the O2 sensor again In case it was faulty, still getting the p0136 code. Other symptoms are poor gas milage and no power, I can barely hit 65 going down a hill with the gas pedal floored

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Answer 1

P0136 02 sensor heater circuit malfunction Bank 1 Sensor 2

P2271 02 sensor signal sensor stuck rich Bank 1 Sensor 2

Running rich condition will definetly rob the engine of power. the 02 sensor is just reporting the condition of the engine. Mechanical condition has to be ruled out, Some of the 1.6 have timing belt that can be off a tooth which can cause the engine to go rich. another is airfilter condition, ? Also the  charging condition.should also be checked

Clean airfilter is important, without a clean airfilter the engine can not breath properly, when you have running rich condition

 Timing belt is important , here a timng belt slipped of it keyway and cause a running rich condition , where the vehicle idled great but under acceleration there was no power.