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Cycle variability in spark-ignition engines is mainly attributable to the occurrence of poor ignited and misfired cycles. The non-ordinary ignited cycles were previously observed to occur when either, the flame did not move away from the electrodes, and therefore had much contact with electrodes, or when large portions of the flame were rapidly convected away from the electrodes and therefore the flame was quenched in the flow field. Cycle variability can also occur due to turbulence or non-homogeneity in the mixture strength. Experiments showed that the degree of the cyclic variability depends very much on the characteristics of the introduced spark, the flow regime in the electrodes' gap, and the spark plug design. In the present work, we investigated the effect of the amount of energy supplied to the spark plug, the law of energy deposition during glow phase, the mean velocity vector in the spark gap and the spark plug orientation, on the mixture lean misfire limit.