Patent ID: 6883476

Claim:
A control system for an internal combustion engine having a variable valve operating mechanism capable of varying at least one of a valve lift and an operation angle of an engine valve continuously, comprising: a detecting device that detects an operating condition of the variable valve operating mechanism and produces a signal representative thereof; and a controller that controls the operating condition of the variable valve operating mechanism in response to the signal from the detecting device; the controller being programmed to determine whether an operation responsiveness of the variable valve operating mechanism is lowered based on the signal from the detecting device and vary operational characteristics of the variable valve operating mechanism when the operation responsiveness of the variable valve operating mechanism is lowered; wherein the variable valve operating mechanism includes an actuator and a control shaft that is driven by the actuator so as to vary in a rotational angle thereof and thereby variably control one of the valve lift and the operation angle, the controller being programmed to determine whether the operation responsiveness of the variable valve operating mechanism is lowered based on a holding energy of the actuator for holding the control shaft at a target rotational angle when a target rotational angle of the control shaft is held constant for a predetermined period of time.