Just recently I started to get a bit of a rough idle, in particular at start up. I never used to get this. My car just turned 212k kms. Does anyone have any ideas what could be the cause. I am thinking that it may be my O2 sensor since it has never been changed since I have owned the car. Anyone else have any ideas? This rough idle at full stop is really starting to bug me. Any comments/ideas would be appreciated.

Brian