What exactly is the purpose of the O2 sensors? I'm mean I can figure out the are "oxygen" sensors, but what role does this play in the exhaust? You hear people with aftermarket headers relocating the O2 sensors and such. Did "back in the day" cars (70's) have these, because I don't recall so?

O2 sensors measure the quantity of oxygen in the exhaust so the computer can correctly add the proper amount of fuel to the engine.
These became prevalent in the 80's when electronic engine management beacame available.

The computer then can fine tune the amount of fuel the engine receives on a continual basis so that the engine operates at peak efficiency & mileage.

O2 sensors measure exhaust temperature only. Nothing else. And the more oxygen you pump in just ahead of the O2 sensor, the hotter the exhaust gets. They call them O2 sensors, but all they are is a thermocouple that measures heat. I think they came along in '81 or '82 with the advent of the computers.

Here is the "What".

http://www.aa1car.com/library/o2sensor.htm

:2ni19wj:

Whoa! THAT was quite thorough! Thank you for the link - always good to learn something about how these monsters work. :goodpost: :thumbsup: