Can a bad o2 sensor cause high idle?

Yes, a bad O2 sensor can cause a high, or rough, idle. The oxygen sensor output is part of the systems that control engine timing, combustion intervals, and the air to fuel ratio. When it starts to go bad, it can cause rough idling, loss of power, hesitation, or stalling. To avoid these issues, the O2 sensor should be replaced every 60,000-90,000 miles.