A method of operating a syngas generator within a desired temperature range, despite a need for intermittent syngas output, involves switching between operating the syngas generator in a rich mode and a lean mode. Operation of the syngas generator in both the rich mode and the lean mode sustains the operating temperature of the syngas generator within that desired temperature range, particularly for non-catalytic reactors. The method of switching from the lean mode to the rich mode of operation can include decreasing the oxygen-to-carbon ratio of reactants supplied to the syngas generator. The flow rate of one or more of the reactant streams supplied to the syngas generator can be actively controlled in order to switch operation of the syngas generator between the rich and lean modes.