I failed to mention that it is a 45k mile car and supposedly a 100k O2 sensor. I also failed to mention that the problem started a day or two after I had changed the spark plugs, air filter, etc. So I probably knocked a vacuum hose loose. The dealer had a change of ownership and the new owner has become ridiculously aggressive (crooked) on service. My sister is afraid to even go into the place. It may take a while but I'll let you know how it goes. Thanks for all the help.