How do you know when your O2 sensor is toast?

[sdg3205]

What are the signs and symptoms of a failing or failed O2 sensor?

[Bitsyncmaster]

They work a long time unless you contaminate them with silicone or your engine runs rich for a long time. The way I would test it is put my wideband LM-2 unit onto the exhaust pipe and read the AFR. I would also guess you would have a hard time adjusting the duty cycle (dwell) using the dwell meter on the FV. For those owners without the test equipment you would have to guess that your mixture is rich or lean. The sensor does not cost much and after you get the original one removed is not to hard to replace. So many just replace them every few years or 20,000 miles.

[sdg3205]

They work a long time unless you contaminate them with silicone or your engine runs rich for a long time. The way I would test it is put my wideband LM-2 unit onto the exhaust pipe and read the AFR. I would also guess you would have a hard time adjusting the duty cycle (dwell) using the dwell meter on the FV. For those owners without the test equipment you would have to guess that your mixture is rich or lean. The sensor does not cost much and after you get the original one removed is not to hard to replace. So many just replace them every few years or 20,000 miles.

Yeah, that's my concern. My car wan rich for who knows how long. It had to be really rich with the lambda system in-operational. Might as well just play it safe and replace it.

[David T]

If the O2 sensor is fouled from running rich you can try the "poor man's" fix. Heat it up with a torch to burn off the fuel residue. It works unless it has been contaminated. If you can't get the Lambda to run "closed loop" and vary the duty cycle it is bad. If you do change the O2 sensor you are supposed to check and adjust the valves and reset the Lambda counter. I also recommend changing the spark plugs and the air and fuel filters. Supposed to be done every 30,000 miles or 30 years!
David Teitelbaum

[DMCMW Dave]

I find that when bad they take a lot longer to light up (i.e. the ECU starts swinging the frequency valve), they don't light up at all, or they will cool off with the engine idling. I've never seen one give out wrong voltages.