Vehicle idle has become an increasing quality concern for automobile manufacturers because of its impact on customer satisfaction. As demand for better fuel economy increases, automobile manufacturers are continuously looking for any benefits from different driving conditions. Combustion variability in spark ignition engines was recognized that the stability of engine at idle is affected by the factors of fuel injection timing, ignition timing and air-fuel ratio. Therefore in this research, the results will be shown the effects of stability and the variations at idle according to fuel injection timing, ignition timing and air-fuel ratio as the basic parameters.