A four-stroke cycle, multi-cylinder reciprocating internal combustion engine has a camshaft phaser for powering an exhaust camshaft and for adjusting timing of the camshaft with respect to the rotational position of the crankshaft so that the cylinders of the engine may be deactivated by adjusting the camshaft timing such that the exhaust valves for each cylinder open and close at points which are approximately symmetrical about a rotational position of the crankshaft at which the direction of motion of the pistons change. The controller also closes an intake port throttle during cylinder deactivation.