Misfire discriminating method for an engine

摘要

A method of discriminating the misfire of a multicylinder engine for each cylinder (FIG. 1 A), comprising the steps of discriminating a cylinder number (#i) at a present combustion stroke (S101); calculating a present momentum at the present combustion stroke, in a period in which no combustive work is done (S105); computing a second momentum at a second stroke preceding the present combustion stroke two times, in a period in which no combustive work is done (S106); averaging the present and second momentums (S107); deriving a first momentum at a first stroke preceding the present combustion stroke one time, in a period in which no combustive work is done (S107); taking a difference between the averaged momentum and the first momentum (S107); setting a misfire judgement level from a map of combustion conditions in a function of said first momentum and engine load data (S108); and comparing the difference with the misfire judgement level (S109), thereby to judge the misfire condition for each cylinder without being affected by a manufactural allowance.