STARTING METHOD OF AIR-FUEL RATIO FEEDBACK IN ELECTRONICALLY CONTROLLED ENGINE

摘要

PURPOSE:To improve drivability, by setting an initial value of warming increase with engine temperature, reducing the value at a prescribed rate for every engine speed and starting feedback control of air-fuel ratio when the value is decreased below a preset value. CONSTITUTION:A CPU56 of an electronic control unit fetches water temperature at starting from a sensor 30 to obtain an initial value of increase from a map and store the value in a RAM56 as a warming increase value. Then interruption by a signal of every one turn of a crank angle sensor 32 subtracts a constant A in accordance with a load condition from a stored warming increase value FWL to compare the subtracted value FWLd with an air-fuel ratio feedback start value FWLf, if FWLd =FWLf, air-fuel ratio feedback control on the basis of an output of an O2 sensor 31 is started. Accordingly, drivability is improved, and worsening of emission, caused at disorder of air-fuel ratio due to the O2 sensor under an insufficient condition of warming and at overrich due to a delay start of feedback control, can be improved.