Thanks to all who responded on this and other posts.

I followed the advice of several people- used SBlaster several times over the course of several days after warming the car up, along with some mechanical stress from impact with a hammer. I wasn't in a hurry.

This morning, beautiful day here in central PA, finally just used a regular 7/8 box wrench (no need to buy or borrow the 6-point) and a little hammer tap and it came off with no problem! What a relief!

After getting the old one out, which had been spliced, I find that one of the heater wires simply _fell_ out of it's crimp connector! I hope I did a better job of crimping then whoever did that last one.

I had bought some ramps, so climbing under and out from under the car was the hardest part- I have a bad back.

The new O2 sensor, the Bosch 13942, came with so little anti-seize (see photo) that I went ahead and bought a tube of the Permatex 1600 degree stuff and used a little. Yea Art, that old sensor looks very different...

I've reset the codes by pulling fuse 6 briefly- now let's see if this makes a difference in the next few days...

Keith
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1991 240 Sedan B230F LH3.1 300K miles