engine running rich

[S13_PoWar]

hey guys i have a 240sx with 163000 miles on da engine. its running a lil rich. i checked everything already besides the o2 sensor. dizzy, wires, maf, plugs still good. if it is da o2 sensor how can u tell its bad and wat brand name should i get? thx

[Doya]

Test the volts coming from the o2 senor, that will tell you if it's bad or not. Bosche is pretty cheap, but if you have the money, I would get a NTK.