Nonlinear control methods for automotive electronic throttle control (ETC) systems are developed using the theory of sliding mode control. The motivation for the use of sliding mode controllers stems from the fact that the throttle valve in our developing ETC is supported for fail-safe by two springs which can be modeled as a nonlinear discontinuous spring. This situation, however, satisfies so called matching condition in the context of the sliding mode control theory, namely the system is insensitive to this disturbance during sliding mode. Two kind of methods to estimate the valve velocity with the measurement of its position, variable structure observer and over-sampling method, are also designed. Experimental results illustrate the effectiveness of the controller and estimators.