I really don’t understand the fundamentals of how they work & why they are used.
Here’s what I think I know: O2 sensors assist the engine computer make minor adjustments to the amount of fuel to deliver to achieve the best mixture. The fuel injection system does most of the work, measuring the air intake with a Mass Airflow Sensor, and metering out the fuel to match, and the O2 sensors are used only to make small incremental changes to fuel delivery, based on the O2 reading. If the mixture is too lean, there’s not enough gas to combine with all the O2, and some O2 will come out the exhaust. No good. If the mixture is too rich, no O2 will come out at all, but some unburned gas will be in the exhaust. Again, no good. Ideally, there’d be just enough gas to burn all the O2, but no more. So it seems like the thing for the engine computer to do is monitor the O2 and if there is no O2 coming out, that means there is too much gas, so give it less gas, but only until the O2 first starts to register, which means there is no enough gas, then give it a little more gas, and continue this process indefinitely.
Is this more or less correct? How come cars in the 70’s didn’t have any O2 sensors? What are the physics of how these sensors work? Do they work when the engine is cold or only when it is hot? Why do some cars have only one O2 sensor, and some care have more than one?
All comments appreciated. Thanks.