PURPOSE: To make an air-fuel ratio in a misfire limitation detectable accurately, by detecting a combustion state before and after the lean side at a time when the air-fuel ratio is changed to the lean side as long as the specified time, while changing the air-fuel ratio to the roch side at a time when a difference of the detected result is more than the specified value.
CONSTITUTION: In case of an air-fuel ratio controller II controlling an air-fuel ratio according to a running state of an internal-combustion engine I, there are provided with a combustion state detecting device II-A and a first lean changing device II-B changing the air-fuel ratio to the lean side as far as the specified value for the specified period long. In addition there is provided with a state difference detecting device II=E which detects a difference of the detected result of the detecting device II-A before and after the time when alteration in the air-fuel ratio by the said device II-B. And, when the state difference detection result is more than the specified value, an overrich changing device II-D changing the air-fuel ratio to the overrich side as much as the specified value by an air-fuel ratio changing device II-f is operated, and when it is less than the specified value, a second lean changing device II-C changing the air-fuel ratio to the lean side at a smaller value than the specified value of the said device II-C is made so as to be operated.
YAMADA HIROATSU
KIGAMI KATSUHIKO
| JPH0526021A | 1993-02-02 |