how can i tell if my O2 sensors are bad without getting a diagnostic, or scan...whichever it is. Im getting about 190 to the tank. I just picked up a fuel filter. And i just changed plugs and wires, opti is also good.

 

I was interested in this too.....so I bought two new ones. I dont really know if there is a way, even with my scanmaster. I replaced one, but I broke the tool trying to get out the second. Im taking it to a shop tomorrow so they can bang on it with air tools.
Good luck ill let you know if mine helped. Also I get like 13.5 mpg per tank, and I smell gas....so hopefully this would be the culprit.

 

replacing them every 50k miles is probably a good idea. unless there are visible signs of damage to the sensor or wiring... you cant "see" a bad one without diagnostic tools. as for judging a bad sensor with a scanner before actually getting DTC error codes would be to make sure the O2s function within thier entire 0-1000mv range. if you find one only ranging from 300-600mv for instance then its not working properly and need replaced.

 

i dont smell gas at all. but i do get about 13.5 mpg, which is a little tough being a poor college student