  We examine a simple, fuel-air, model of combustion in a spark ignition (si)
engine with indirect injection. In our two fluid model, variations of fuel mass
burned in cycle sequences appear due to stochastic fluctuations of a fuel feed
amount. We have shown that a small amplitude of these fluctuations affects
considerably the stability of a combustion process strongly depending on the
quality of air-fuel mixture. The largest influence was found in the limit of a
lean combustion. The possible effect of nonlinearities in the combustion
process has been also discussed.
