Roberto, the set screw is not the correct way to adjust the idle on the M20. that screw is only designed as a stop so the pressure of the butterfly valve is on that and not the disk inside preventing the high tension springs from closing.
the correct way is to clean or replace the idle control valve. it couldnt be any more black and white.
please dont post if you dont know what you are talking about. certainly no oil pump code on an M20 engine either. infact hardly any codes at all