Method for diagnosing air intake throttle actuators for internal combustion engines

A method for diagnosing an air intake throttle with a spring activated throttle actuator, on an electronic controlled internal combustion engine system including an electronic control unit (ECU) with memory, a battery electrically connected to said engine and an ignition switch for connecting said battery to said engine and supplying current, comprising engaging the ignition switch to close a circuit between said battery and said engine; applying a first predetermined voltage to an air intake throttle plate actuator and determining a first period of throttle response time elapsed from a full open throttle position to a full close throttle position for a first throttle velocity; discontinuing application of said first predetermined voltage to said air intake throttle actuator and determining a second period of throttle response time elapsed from a full close throttle position to a full open throttle position for a second throttle velocity; applying a second voltage to said air intake throttle plate actuator and determining a third period of throttle response time elapsed from a full open throttle position to a full close throttle position for a third throttle velocity; and determining a fourth period of throttle response time elapsed from a full close throttle position to a full open throttle position with no voltage applied to the throttle plate actuator for a fourth throttle velocity.