quick question- if an 02 sensor is bad- will the engine run rich? what about if there is an exhaust leak before the snesor? will excess gass be pumped into engine? thanks- 1994 pick 3.0 v6

 

if there is a leak before the sensor, it will lean out what the sensor sees, causing the motor to run rich. if the sensor is bad, usually the computer defaults to a "one-size fits all" configuration which i believe is on the lean side.