Minimization of the carbon dioxide and harmful pollutants emissions and maximization of fuel economy for the lean-burn spark ignition (SI) engines significantly rely on precise air-fuel ratio (AFR) control. However, the main challenge of AFR control is the large time-varying delay which exists in lean-burn engines. Since the system is usually subject to external disturbances and uncertainties, a high level of robustness in the AFR control design has to be considered. Herein, a fuzzy sliding-mode control (FSMC) technique is proposed to track the desired AFR in the presence of periodic disturbances. The proposed method is model free and does not need any system characteristics. Based on the fuzzy system input-output data, two scaling factors are first employed to normalize the sliding surface and its derivative. According to the concept of the if-then rule, an appropriate rule table for the logic system is designed. Finally, the feasibility and effectiveness of the proposed control scheme are evaluated under various operating conditions.