The problems causing idle combustion variability are identified. Photographic evidence identifying the various types of ignition kernel growth which influence variability, along with variations in residual gas composition are identified. Combustion variability is quantified in terms of peak cylinder pressure and IMEP variation. The reduction of cyclic variability achievable through the partial spatial decomposition of the fuel is identified. Significant eliminations (about 80% reduction) in idle cyclic variability are reported through this novel technique.