Ok... so while i am idling the car sometimes drops below 500 rpms and feels like its gonna die out but then jumps back up.. it does this all the time while stopped at a light.. i am also getting a code 13.. just wondering if a bad o2 sensor could cause this or if there is something else i should look at.. thanks

 

Yes, a bad O2 sensor can cause this. There are other reasons, but we already know that it is bad based on the code you are getting. I would start there.