An internal combustion engine includes neighboring main and auxiliary combustion chambers that are separated by a partition wall including a communicating passage. Ignition of an air/fuel mixture in the auxiliary combustion chamber produces a fuel torch that is jetted into an air/fuel mixture in the main combustion chamber. Under a predetermined operation condition, timing for opening an intake valve is retarded relative to both the timing for closing an exhaust valve and the timing for top dead center of a piston on an exhaust stroke. By retarding the timing for opening the intake valve, residual gas in the auxiliary combustion that is left over from a previous cycle can be reduced.