The O2 sensor is original to the car. I think I will order a Delco sensor from GMpartsdirect and new AC Delco plugs and go from there.

Thanks for all the advice.

A couple more questions. I looked at 3 plugs and they all seemed to look nornal at the tips. Light beige in color. Dry, no signs of oil. If the O2 sensor were bad and causing the car to run rich, wouldn't the plug tips looked sooty black? I hate to buy an O2 sensor if that'* not it.

Also, how do I reset the computer that the last respondent described? I've never done that before.

Thanks,

Mike

Sounds like your a frugal person that doesn't like to spend money for nothing (like me).
You are correct on the plugs keep them for now.
Try something simple like fuel injector cleaner or changing your brand of gas.
The new ethanol mix is killing everyones mileage.
If this doesnt work then procede to the 02. The best think would be if a friend
had a scan tool he could tell you if it were bad before you clunk down the money.
To reset the PCM you simply pull the fuse for 3 min. to clear it or disconnect
the neg. batt. terminal.

Dirty injectors will affect perfromance, not mileage. A clogged injector is not delivering enough fuel. A low-mileage condition means he'* running rich, not lean.

If your O2 sensor is over 60k miles old, replace it. I gaurantee it'* weak, and is contributing to your problem at the very least. A weak O2 can also contribute to the early death of a catalytic converter.

Yes but the injector cleaner not only cleans the injectors, it cleans the intake and
exhaust valves which improves compression. Also cleans the 02 sensor and
helps keep the cat flowing smoothly.
If the PCM senses a lean condition due to clogged injectors what do you think it is
going to do? Increase fuel with an already poor spray pattern which causes an
incomplete burn.
An inexpensive way to check the 02 is to remove it like you would a spark
plug and inspect it. If its chalky white at the tip your good to go.
If its charcoal brown or black its toast..........Change it.

I'm starting to get the creeps about Bosch.
I have one in my 96.