The mechanic was a pretty highly regarded one. He diagnosed the problem as a bad oxygen sensor. The problem was, I was on a trip and did not have time to wait for the part and so he rigged up a bypass switch. After that, the car ran OK for months, but then began running worse until it would finally barely go at all with weak power and frequent episodes of almost dying. Then, I disconnected the computer and it runs much better but a bit rough.

I know, I know - I should have replaced the oxygen sensor right away, but the car is a spare and I was willing to live with the bypass until it began running badly again.

I am wondering now if I should buy an oxygen sensor alone and try that or go ahead and get an oxygen sensor and computer. Or could there be something else?

Thanks!