A few days ago I started to research auto repair and started with the engine (as you do). I have a question about the engine power and the relation to upstream O2 sensor.
If I understand things correctly, a 14.7:1 fuel ratio is attempted. The MAF combines with IAT and MAP to calculate the air in, and the computer adjusts fuel input accordingly. The upstream O2 reads the air out to the exhaust to see how well the computer did and feeds back, so that adjustments can be made via the fuel trim. If I understand this correctly, it makes sense.
Where it gets unclear to me is: the upstream O2 sensor voltage is a result of measured oxygen. This voltage fluctuates as if it is on a sin wave. This means that the engine must be oscillating the input of air or fuel to produce this result in the O2 sensor?
Is the computer actually continually oscillating the POWER being output by the engine and we just do not notice it because it happens so fast?
I would have expected and increase in fuel injection would correlate directly to an increase in power which would be felt.