Control system for cylinder cutoff internal combustion engine

In a control system for an internal combustion engine (10) having a plurality of cylinders and mounted on a vehicle, in which the engine operation is switched based on the throttle opening ¸TH between a full-cylinder operation in which all of the cylinders are operative and a cut-off cylinder operation in which some of the cylinders are inoperative, and a running control including a cruise control in which the vehicle runs at a desired vehicle velocity (VD) or a preceding vehicle follow-up control in which the vehicle runs at a desired vehicle velocity (VD) to maintain a desired inter-vehicle distance (DD) from a preceding vehicle are conducted. In the system, an acceleration suppression control is conducted if the engine operation is switched from the cut-off cylinder operation to the full-cylinder operation when the running control is in progress (S200 to S230). With this, sharp or drastic acceleration accompanying torque fluctuation is effectively avoided, when the engine operation is switched to the full-cylinder operation.