INTERNAL COMBUSTION ENGINE WITH CONTROL UNIT

An engine has a LPL-EGR mechanism that recirculates low-pressure EGR gas from the downstream of a NSR catalyst in an exhaust gas emission system to an intake air system via a EGR cooler. A NOx-storage level is calculated for a low-temperature NOx-storing material and a high-temperature NOx-storing material carried on the NSR catalyst (step ST6). When the temperature of the NSR catalyst has risen quickly, a NOx-reducing process is carried out if it is predicted that most of the NOx released by the low-temperature NOx-storing material is not stored by the high-temperature NOx-storing material, hence escaping from the NSR catalyst (step ST9). The NOx-reducing process reduces the amount of NOx flowing into the LPL-EGR mechanism and restrains an aqueous acid solution from being produced from NOx, thereby preventing corrosion of the EGR cooler.