i have a 2000 honda civic si, it does not have the second o2 sensor, the wires are there but no o2 sensor. it has a idle problem where it fluctuates up and down when warm. ive cleaned the iacv and throttle body. could i just need to buy and put in the o2 sensor and that would fix my idle problem? what do you all think?

 

your car needs both O2 sensors to be functioning in order for it to run properly. Not only does it control your emissions, but you have a HOLE in your exhaust where your O2 sensor should be. This alone will effect your car's performance.