A method of controlling a variable valve actuation system is provided. A
cam assembly is operated to move an intake valve between a first position
where the intake valve blocks a flow of fluid and a second position where
the intake valve allows a flow of fluid. At least one operating parameter
of the engine is sensed. A valve actuation period is determined based on
the at least one operating parameter. A valve actuator is engaged with
the intake valve to prevent the intake valve from returning to the first
position in response to operation of the cam assembly. The valve actuator
is released to allow the intake valve to return to the first position at
the end of the determined valve actuation period.