Means and method of operating an internal combustion engine

The present invention relates to a method for operating an internal combustion engine, in particular a passenger car, comprising the steps of: Determining (S20) a combustion air ratio (λ); Determining (S20) a deviation (Δλ) of the combustion air ratio (λ) of a particular predetermined or learned, the target air-fuel ratio (λ and Detecting (S30) a self-ignition of the internal combustion engine based on the determined deviation (Δλ).