1995 Honda City oxygen sensor

Engine Mechanical problem
1995 Honda City 4 cyl Two Wheel Drive Manual? Miles

ok I have a 95 honda civic dx 1.5 vtec. I recently took it to get smoged and the guy told me I was passing too much gas. He then said he thinks I have a bad sensor. Im assuming he ment o2 sensor but im not sure. I have a little bit of rough, choppy idle.I smell gas every time I turn on my car from the exhaust pipe and it sounds like its missing when im parked. At times it almost feels like it wants to stall but it never has. What are the main symtoms of a bad sensor? Do I have a bad o2 sensor? Thaaaank you in advance people!