Hey, had to replace a upstream O2 sensor 4-5 months ago. just had the service engine soon light come on had code 0135 and 04?? one was for the O2 sensor up stream and the otherwise the canister vent valve. car started bucking at lower rpm. seems running 55 and start up a grade or start to push the accelerator and it will buck, feels like a bad miss. runs fine if you get above 2000 rpm, and won't do it if Cruze is on. Any Ideas? I repaired the valve and looked at the O2 sensor. light is now gone! but still doing the bucking.