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Re: What are the symptoms of bad O2 sensor? (archive)

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Posted by Wayne McKay on October 10, 2001 at 15:23:43:

In Reply to: What are the symptoms of bad O2 sensor? posted by Adrian Lee on October 09, 2001 at 16:29:53:

The sensors we have are 'two-state' type. The output voltage flip-flops back and forth between about 0.2V and 0.8V as the exhaust gas analysis flips back and forth across an ideal stoichiometric burn. The sensor has a built in heater circuit to maintain a minimum operating temperature. The response time begins to slow down in sensors that have been subjected to high temperatures for too long (running rich) - so much so that they cannot properly keep the feedback system stable (i.e. by the time the DME gets the information from the sensor the system has long since gone 'off the page'). Another common problem results from failure of the heater causing the sensor to operate outside of its normal limits. I am sure there are other things but that is about all I know about them so far.

'88 750iL

My car starts rough. It was parked for 10days. I checked the engine code since the "check engine" light came on. It was a O2 sensor. I just want to be sure b4 I replace the sensor.
Thanks for your help.

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