Funny - I was having similar problems and closely watching this post...I
> replaced the O2 sensor and found the symptoms returning a few days
> later...stuttering, stalling, running rich, smoke, etc.  After unplugging
> the O2 sensor I was able to drive for about 40 kms before the problems
> started again.  Ended up cleaning up all the ground wire connections in the
> engine bay and that has been the difference so far.
>

>  Living in the Pacific Northwest it is now the rainy season and it my
> guess the excessive moisture and cool temperatures weaken strong ground
> contact.
>

BT