Synth

My car is running extremely rich after a rebuild, and I want to check if I have a bad O2 sensor.

I was planning on unplugging the connector in the O2 wiring harness and see if the car runs richer. ( I have a WBO2 to monitor it)

Is this a valid way to check that the O2 sensor works, or is there a better way?

Thanks!

p.s. Yes, I searched

Mike Lindsey

Yes. Unplug the factory O2 and you should see the WBO2 a/f change. That doesn't mean the sensor is working accurately though. They degrade then die. What's probably better to do is un-plug the factory sensor with car running and watch the WB. Let's say your a/f is in the low 13's with the sensor unplugged, and you plugged it in and it goes to 14.7 and hangs around that number closely, then I would say it's probably good. Sensor needs to heat up before the DME will look at it so give it a minute or two once plugged back in. Blip the throttle a couple of times and make sure it comes back to
14.7ish.

reno808

Voltmeter

quinnfiske

I replaced mine after failing an emission test. Car ran great, but I failed NOx. so I replaced it With the new O2 sensor it passed NOx but failed CO and HC. An AFM adjustment cured that. So I would conclude that they can drift after a while and should be replaced at some interval, like spark plugs etc. How often? Maybe 30K miles, or 60K who knows?