PURPOSE: To detect no deviation between air-fuel ratios of cylinders and prevent puripying characteristcs from deteriorated due to deviation of air-fuel ratio from proper value by increasingly raising the amount of variation in ratio of air-fuel mixture for a specified period from the switching time two signals produced according to a sepcific concentration of composition of exhaust gas.
CONSTITUTION: An air-fuel ratio feedback compensating coefficient FAF is skipped by RS1+RS2 at the change point between rich a mixture signal and lean mixture signal and the amount of the skip is maintained until fuel injection is performed by (n) times from the change point and when the frequency is over (n), the quantity of skip becomes RS1. When a signal is changed, a high value of RS1+RS2 is exhibited in the early time, however, the skip quantity becomes a normal value RS1. Since the skip quantity is great at the change point, the O2 sensor will not respond to deviation between th air-fuel ratios of cylinders, the detecting signal of the O2 sensor is stabilized and controlled ari-fuel ratio is also stabilized by feedback so that purifying performance of a three-way catalytic converter.
DOUMIYOU HIROYUKI
SHIRATANI KAZUHIKO
