The simulation of combustion in the internal combustion engines (ICE) is very important for an accurate prediction of engine performance and pollutant formation. These engines simulation help to gain a better understanding of the coupling between the various physical and chemical processes. The objective of the present paper is to study turbulent combustion in IC engine. A lagrangian eulerian model coupled with presumed pdf is used to study the problems of chemical kinetics (and), while the k-ε model is used for the modeling of the turbulence.We got the reduced mechanism through the reduction of detailed mechanism of the methane (GRI 3.0) combustion by using the Principal Component Analyses (PCAF). It is considered the first point for the application of the Computational Singular Perturbation method (CSP). We used this method (CSP) to reduce the detailed mechanism of the methane that is already reduced by PCAF to a mechanism containing 9-Steps. The validation of this reduced mechanism has been made by the comparison between the results of the reduced and detailed mechanisms of methane GRI 3.0; this comparison for major species, pollutants species and temperature at high pressure and lean mixture.The results of computations with the present model are compared with the experimental and simulation GRI 3.0. These comparisons between the modeling and the experiments show a good agreement for emission pollutant, major species, pressure, and temperature. We, also, studied the effect of operating conditions such as equivalent ratio and crank angle rotation on the formation of pollutants emissions. This parametric study showed the sensitivity of variations in operating parameters of the engine on the prediction of emissions pollutant (CO, NO, CO2 and HC), the pressure and temperature in the combustion chamber; which has a positive point of the model elaborated.