Is this a manual transmission car?

There was an incorrect O2 sensor part number posted on many sites (even FCP Groton), for many years, for the '96 wagon manual.

I ended up with the wrong sensor, ws not able to figure out the problem before I destroyed my engine with the same symptoms you are describing.

I know the number for the sensor on FCP Groton is now correct, so if you did not use the part number listed there and you have a manual transmissioned car, check it out right away.

Also, look for vacuum leaks which can cause the computer to compensate with an overly rich mixture. I just use a rubber hose slipped on to the end of a (unlit) propane torch and point the other end of the hose to every possible vacuum interface. If you hear the idle rise every time you point the hose at a particular interface, you've found a problem.

Ken

Check the FAQ's for O2 sensor info. I believe reading a while back where some parts suppliers computer systems, and they all share the same one, don't have the right one lsited.