Method for detecting combustion failure by filtering

A method of detecting misfires of a mixture between a fuel and an oxidizing agent, in any one of the cylinders of an internal combustion engine having multiple-stroke operating cycles, such as two-stroke or four-stroke cycles, this method comprising the following steps:

• a) during at least some of the combustion phases in at least one of the cylinders, at an instant (t) of the engine operating cycles, a current value of an index In(t) representative of operating irregularities in the engine stroke is calculated,
• b) while the engine is operating, and on the basis of the current value at the instant t of the index In(t), the current value at the same instant t of an observation function G(t) is calculated, this function being a function of an instantaneous discrepancy between said current value at the instant t of the index In(t) and an estimated reference value Īn+i(t) illustrative of this index at a different instant,
• c) the current value of G(t) is compared with a predetermined threshold (S) dependent on the engine load (C) and/or speed (N), and
• d) a misfire is diagnosed when the value of G(t) crosses the threshold (S), characterized in that:
• the observation function G(t) is such that:
• G(t)=Īn(t)−In(t),
• with Īn(t)=Īn+i(t)+a×En(t)
• Īn(t) corresponding to a value representative of the index In(t) after the values of this index that lie outside a predetermined permissible discrepancy (BC) have been excluded and/or weighted and where a is a correction coefficient dependent on |En(t)|,
• and En(t)=In(t)−Īn+i(t), i being an operating cycle different from n, En(t) being an expression of the instantaneous discrepancy between said current value at the instant t of the index In(t) and the corresponding reference value Īn+i(t) illustrative of this index at a different instant.