almost done with my engine swap and i pulled out the o2 sensor by the exhaust manifold to have a look bec ive been advised that i should probably change them. unfortunately im not too sure what im looking at when it comes to figuring out if the sensor is shot and needs to be replaced. anyone have a pic of a shot o2 sensor or have an idea of what characteristics a bad one should have? i have 80k miles on it and i think they are still original. i know i had antifreeze leaking through everything due to a crack in the head and ive read that antifreeze alone can damage the o2 sensor. my sensor is rough to the touch greyish brown color..kind of dusty, certainly doesnt look new. Also, given the fact that antifreeze may have contacted that one, the chances of the fluid gettin past the cat and damaging the second sensor should be low correct?
If I remember correctly, the O2 sensor can only be tested proffessionally, meaning there is no whay for you to be SURE it is working. Having said that, you can always hook up a voltmeter with a long cable and see the voltage that it reads.
For this, all you have to do is connect a wire long enough from the O2 plug to your digital multimeter inside where your passenger can read it while testing. Just make sure that that wire never touches ground as it will damage the sensor. Ground the negative wire so that you can read voltages. You will find 4 wires on the O2 sensor. Two are for the heater + & - and the other two are ground for the sensor and output to the ECU. One positive will have 12v for the heater and the other will be at .450 volts when the engine is cold and in open loop mode will running.
After reaching operational temperature, the reading will begin to start changing from near 0v to 1v. This happens fast, so be ready for it (in other words, have someone read them to you as you drive). If voltage changes as described, all is as it should. If you do not get a change by the time your thermostat has opened, then there is a problem and could be you are running too cold a one so it is staying in open loop mode, or the O2 sensor is shot.
The range is as follows: 3mV being the leanest, 1V being the richest.
If I were you, though, not knowing the condition of your current one, I would change it... That way I would be sure it is running good. A bad O2 sensor means you are wasting fuel, and with the prices of gas today, I prefer to know I am not wasting anything!
