An engine includes an intake manifold and an air-induction system configured to deliver air to the intake manifold. The air-induction system includes a throttle attached to the intake manifold, an air cleaner, conduit connecting between the air cleaner and the throttle to create a flow path therebetween, and a valve disposed in the flow path to be upstream of the throttle and downstream the air cleaner. The valve has a closed position in which the flow path is blocked to hold hydrocarbons within the intake manifold and inhibit emission therefrom and has an open position in which the flow path is unimpeded.