02 sensor information

i am a mileage snob, and was reading the current thread with some interest. my car has 180k and no work history, so i was thinking maybe the 02 sensor could use a little TLC.

my FSM says nothing about it, presumably because emissions stuff is only covered in the *emissions* FSM. (siiigh). my chilton's gives voltages and resistances to look for, but reccomends that you first pull the sensor and check for residues on it. however, i do not have the right size wrench for the sensor (looks like 21mm or so??) and would prefer not to buy another (im on a roadtrip. wont be home for weeks.)

two questions:

1) if the voltages and resistances check out, is it still necessary to check for sensor residues? or does that just provide insight into potential other problems in the emission system?

2) what is the lead layout on the sensor connector? chilton's mentions power to the heating element, ground, and signal return. there are four leads on my connector, and i dont see any indicator of which is which. anybody help me out?

thanks,
anthony

well checking the ohms and resistance will only check to see if the sensor itself works, but if its old and dirty and just worn, but still works, it stil may need to be replaced. I believe o2 sensors replacement intervals are 100k maybe even 80k. I had to repalce mine at 140k, but it was really really bad. and yeah it is like 21 or 22mm. but you can go to autozone or something like that and buy a o2 sensor removal tool. which is basically 21 or 22mm socket type thing that you can use to take it out. but even with two different types of those, I couldnt get mine out and had to replace the wole exhaust manifold just to replace the sensor. and even with the exhaust manifold out of the car with one of my lrge friends standing on it to hold it still, with a breaker bar and extension putting all my weight on it, I still couldnt get out my or sensor out of my exhaust mani. it was fucking nuts, so long being in there and getting so hot, it welded itself in there. hope that didnt happen to you.

well checking the ohms and resistance will only check to see if the sensor itself works, but if its old and dirty and just worn, but still works, it stil may need to be replaced. I believe o2 sensors replacement intervals are 100k maybe even 80k. I had to repalce mine at 140k, but it was really really bad.

well, i borrowed the sensor removal tool from a local autozone. it came out extremely easily for me, thank goodness. in fact, easier than any other single fastener in my entire rusty car. maybe this means it was replaced recently..

anyways, it had a white crust on it. very thin. doesnt look like it would impair air flow through the sensor. my manual suggests this would indicate an internal coolant leak. is that necessarily so? if so, i assume fixing the coolant leak would be a big pain in the butt, and that replacing the o2 sensor would be a waste of time (just be mucked up again).

my coolant level has not perceptibly changed in the last few months, so its obviously not much.

ideas?

anthony