Yup. It's either the knock sensor not doing its job (can't be cleaned... it's a vibration sensor, not a fluid sensor) or the O2 sensor not adjusting properly.

O2 sensors can go bad due to deposits, but it's not that common. You can clean it if you have a socket wrench for O2 sensors (they have a notch so they don't catch on the sensor wire) or use an open wrench with a lot of patience. Check if there are deposits on it... you can clean it off with a rag. But usually, it isn't this.