[mianos]

Yes, it's a closed loop. The O2 sensor in the exhaust rapidly adjusts the mixture.

The whole 'learning' the air fuel mixture to adjust the stoichiometric ratio over a longer period of time does not make any sense. You have the air mass, O2, fuel, temperature and sometimes more, you can calculate the mixture near instantly.

Maybe someone way back said you have to warm the car up and that takes a few minutes. Modern fuel maps achieve a fair idle from near dead cold. It's a solved problem.