The oxygen sensor should be fine if you're not getting any CEL codes. If the car is consistently idling low when warmed up your problem is either a bad idle air control valve (IACV) or your idle adjusting screw is set a bit too low. Here's how you adjust the idle screw, you can see if that helps.




(These are from a 1993 Helms manual so just go by what it says for the B17A1)