Hi, i have chevy aveo Model 2008. in summer when driving about 1 hour the RPM will not be stable when you change the gear to N, FYI Manual Gear not automatic i have change the fuel pump and the injectors and sparks and the TPS and MAP Sensor O2 Sensor. after driving 1 hour feel the engine performance is down also the car starting difficult . when unplug the O2 Sensor the performance will back to normal but will waste much fuel, the RPM up and down when idle. anyone have this problem or anyone know what is wrong with my car?

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