02 sensors will lose all voltage?

If you sit at idle for a long time o2 sensors will act up voltage Wize. When it gets hot out as far as temperature, I've noticed o2 sensors will lose all voltage to two of them on bank 2 or all four of them at times going into open loop. If you let up on the throttle and go back on and throttle they will come back on back to close loop this will happen on the highway anyway and then go back off do same thing over and over and over. This won't work in town it will just buck and Carrie On I've noticed the night time or cooler out it won't do it at all I was thinking ECM? This just got gradually got worse and worse it's pretty bad now of course it's 100° out.