O2 sensor wires

[2stroke]

I was doing some research on exactly how an O2 sensor works, being as I just replaced mine, and was curious. By the way, if you ever get a code for a bad O2, check that both are tight. One of mine wan't even threaded in all the way, and I unscrewed it by hand. Its the first time I've seen it happen, and the result was one bank lean (white/red o2 sensor filament) and the other bank rich (black o2 sensor filament).

Anyway I was reading and it stated that O2 sensors actually breath through their wires to prevent ash and other buildup. Because of this, the site stated to never use any grease on the connectors. I always use di-electric grease on electrical connections. I could not find a reference to this from a reputable source, and the directions that came with my sensors said nothing about it. In my mind, it seems like total garbage, but maybe I'm unintentionally shortening sensor life. I can't remember the last time I had one actually go bad either.

Thoughts?

link to one of the few sources:
http://www.autotap.com/techlibrary/understanding_oxygen_sensors.asp

 

[natenkiki2004]

I think that's bunk. The temp is so hot there, if it breathed through the wires, it would straight up melt them. O2 sensors don't breathe. The reason they're so expensive is that they're built like a Catalytic Converter, they have a catalyst inside that reacts to oxygen to generate a voltage. This voltage is sent to the computer and with some math, it can detect how much oxygen is in the tailpipe.

When the sensor detects voltage, the computer adds a pinch more fuel, the sensor then detects no oxygen (rich) and the computer pulls back on the fuel. This is what's described as switching. The O2 sensor is constantly switching rich/lean because the computer is constantly adjusting fuel in concert with it. Conditions change drastically for air/fuel and you cannot have a constant steady supply of fuel, it wouldn't work. So the computer switches the engine from rich to lean and verifies that the O2 sensor follows that rhythm, if it doesn't, it throws a code and ignores the O2 sensor data.

Just because you get a code for the O2 sensor doesn't mean it's faulty. What else can cause the O2 sensor to stop switching? Vacuum leaks, bad MAF, bad TPS signal, leaking/non-functioning injector, no spark/combustion (the oxygen that would have been burned is now in the tailpipe).


There's a lot to think about and diagnose. If you're truly interested in this kind of stuff, check out ScannerDanner on YouTube and find his videos on O2 sensors, it's really mind-opening. There's definitive tests you can do that rule out MAF and other things before even opening the hood. Granted, most of his stuff is only applicable to OBD-II systems but ours works the same way... we just can't see fuel trim and other sensor data.

 

[vq5speed]

You basically are saying the same thing the link says you just explained it more detail.

I was interested in this breathing thing I never new this. I looked at a few cut away diagrams of a O2 sensor and they do show it does need to breath. Older sensors had a hole where newer one now just breath through the wire connector they call reference air.

 

[natenkiki2004]

Hmmm, I have never seen that. Didn't see any kind of a breather on the O2 that I removed from my Ex. It looked pretty sealed up. Maybe the air is just for the heater so it can breathe and not overheat? I find that really odd though. It's still got to be sealed for the exhaust otherwise newer cars with downstream O2 sensors wouldn't like that.

 

[Number4]

This guy explains in a way anyone can understand.
https://m.youtube.com/watch?v=5WnM_NsOtd8&layout=mobile&client=mv-google
Don't know about the breathing. It certainly isn't breathing through the connector or harness portion.

 

[natenkiki2004]

Schrodingers Box is a good channel. Once you understand fuel trim, have a look at diagnosing a 1998 Ford O2 sensor from ScannerDanner:
https://www.youtube.com/watch?v=PYFQ3Y4eFWY