Did a routine maint. on my '91 Olds Regency Elite. Replaced plugs, wires, filters etc.... Also replaced the O2 sensor, and because it had been idling rough while cold I replaced teh temp sensor. After I did all this I began noticing that if the car sat still at idle for more than 3 or 4 minutes the check engine light would come an, and the engine would begin to stumble a bit. I checked the codes and it came back to a low voltage on the O2 sensor. Thinking the O2 was bad, I replaced it again.....to no avail.....it still does the same thing. I've never seen it do this before in all the years I've had it. Any thoughts anyone?

what brand o2 did you install?

is the connector dirty or corroded?