Patent US 4,837,698

A novel method of controlling air-fuel ratio for an internal combustion engine is disclosed, which comprises a memory area for holding regional compensation factors used for air-fuel ratio control, a memory area for holding new regional compensation factors obtained by learning, and a memory area for holding regional compensation factors based on the result of the learning immediately before the latest learning, thus rationalizing the new setting and updating proceses of regional compensation factors according to the result of learning.