Despite being one of the fastest growing alternative fuel sources, little attention has been given to control of the air fuel ratio at the point of combustion in liquefied petroleum gas (LPG) engines. In this paper a mean value engine model is presented for LPG throttle body injected engines. Based on this model, a control algorithm capable of adapting to errors in both the fuel and air systems is proposed to ensure accurate stoichiometric fuel injection control. Simulation results are presented to validate the proposed approach.