I took out both O2 sensors and cleaned them, the down pipe one has been replaced at some time but the rear one looks like it`s the original from 1997 :]
After cleaning them I noticed while in sitting in traffic it idles a lot smoother sometimes so smooth I thought it stalled...
With that said the rear one has been there for many years and just cleaning the soot off made a noticeable difference, but would a new one give any better temp reading? I`m not techy with electrical and the wires don`t feel crispy or have any signs wear just the outside housing is as old looking as the stock muffler no doubt the original one from 97...
Not sure what that inside prong of the sensor is made of, ceramic ?
Thanks for your time, Cheers
Edit : Forgot to mention I reset the ECU...
The sensing element is either a titania or zirconia porous ceramic, and the unit compares the oxygen content of exhaust gas and ambient air. (I don't recall which is which, but I think it's the zirconia ceramic that generates a voltage signal - being an "air battery" - and the titania that generates a variable resistance - which is used as a "voltage divider" on a reference voltage signal.)
The porous ceramic cannot
be cleaned, and it eventually clogs up with carbon.
As far as service life? Spec for OBD-II is 60,000 miles for all sensors - field reports show useful life of 60,000-75,000 miles for the "upstream" sensors and up to 100,000 miles for the "downstream" sensors.
OBD-I is usually spec'd to about 75,000-80,000 miles, I've seen them go out to 110,000-120,000 or so.
Pre-OBD? I don't recall the spec life, but the longest-lasting HEGO I've seen still generating a useful signal had 220,000 miles on it...
(As the control systems get newer, they're pickier about the signals generated.)