[Beav]

Let me confuse the heck outta all of ya's. The engine basically runs from info gathered by the other sensors. The O2 sensor(s) tell the computer if the final outcome is good. If the final outcome is not good the computer compensates by varying timing (providing there's no bad reports from the knock sensor(s), adjusting the pulse width at the injectors, etc. Now the problem becomes is a bad reading the result of a bad O2 sensor or is something else causing a problem beyond the computer's ability to compensate? And for those of you with OBDII models the rear O2 sensors exist only to watch the effectiveness of the catalytic convertor.

O2 sensors are typically very reliable, however they don't tolerate being subjected to abnormal enviroments very well. Silicone sealers not labeled "O2 safe" will kill them instantly, excessive oil burning, excessive fuel will cause them to melt, as will a clogged exhaust. A coolant leak can cause anti-freeze to ruin them. I strongly suspect that those prone to spray can after can of injector/carb cleaner, etc. down the engine's throat aren't doing the sensors much good either.

Then there's the 'normal wear and tear' factor. If the car has always run perfectly chances are they'll last as long as the car.

Best bet is to use a good digital DVOM meter (I wouldn't trust the in-car meter you have to report as fast as the sensor does) and backprobe the suspect sensor's connection. The info gained through a computer connection tends to be sluggish, especially for those that use generic OBDII readers.The sensors will be sluggish until warmed a bit, usually 30-40 seconds should be sufficient. Once warmed the readings should change fairly quickly, ranging from .01 - .99 volt. The readings will vary faster as the engine approaches normal operating temperature.

If your in-car gauge is accurate, it would appear to me that something else is causing a problem.