Abstract: In an internal combustion engine having a plurality of cylinders, an air-fuel ratio signal is sampled and held for a selected cylinder, and an air-fuel ratio feedback amount is calculated in accordance with the sampled and held air-fuel ratio signal. During a learning control, a cylinder on the leanest side is determined by changing the selected cylinder. During a feedback control without the learning control, the selected cylinder is fixed as the cylinder on the leanest side.

Abstract: Stabilizers for chlorine-containing resins, derived from pentaerythritol and/or polypentaerythritols, which comprises at least one member selected from (1), a dehydration condensation product of pentaerythritol or polypentaerythritol, (2) a partial esterification product of pentaerythritol, polypentaerythritol or the dehydration condensation product with an aliphatic polybasic acid, (3) a partial esterification product of polypentaerythritol or the dehydration condensation product with an aromatic mono- or poly-basic acid, and (4) a partial esterification product of pentaerythritol, polypentaerythritol or the dehydration condensation product with an aliphatic or aromatic polybasic acid and a higher fatty acid. The stabilizers have the excellent effect of stabilizing chlorine-containing resins, and particularly the combination use with known organic zinc salt stabilizers brings excellent results.