Control system for internal combustion engine

A control system for controlling an internal combustion engine having an exhaust passage and an intake passage, said control system comprising:

• an exhaust gas recirculation mechanism having an exhaust gas recirculation passage connected between said exhaust passage and said intake passage, and an exhaust gas recirculation valve provided in said exhaust gas recirculation passage for controlling an exhaust gas amount to be recirculated from said exhaust passage through said exhaust gas recirculation passage to said intake passage;
• a control module for calculating at least one control parameter of said engine based upon operating conditions of said engine including an open/closed condition of said exhaust gas recirculation valve and for controlling said engine by using the calculated at least one control parameter;
• a fuel supply interrupting module for interrupting the supply of fuel to said engine in a decelerating operation of said engine;
• a pressure sensor for detecting the intake pressure in said intake passage;
• a pressure change calculating module for calculating the amount of change in the intake pressure between when opening said exhaust gas recirculation valve and when closing said exhaust gas recirculation valve while in a fuel-cut operation where the fuel supply to said engine is interrupted by said fuel supply interrupting module;
• and
• an abnormality determining module for determining the abnormality of said exhaust gas recirculation mechanism according to the amount of change in said intake pressure;
• said control module controlling said engine by using said at least one control parameter suitable for a closed condition of said exhaust gas recirculation valve during a predetermined time period from the time of first opening of said exhaust gas recirculation valve after finishing the abnormality determination by said abnormality determining module.

A control method for controlling an internal combustion engine being provided with an exhaust passage, an intake passage, an exhaust gas recirculation mechanism having an exhaust gas recirculation passage connected between said exhaust passage and said intake passage, and an exhaust gas recirculation valve provided in said exhaust gas recirculation passage for controlling an exhaust gas amount to be recirculated from said exhaust passage through said exhaust gas recirculation passage to said intake passage, said control method comprising the steps of:

• a) calculating at least one control parameter of said engine based upon operating conditions of said engine including an open/closed condition of said exhaust gas recirculation valve;
• b) controlling said engine by using the calculated at least one control parameter;
• c) interrupting the supply of fuel to said engine in a decelerating operation of said engine;
• d) detecting an intake pressure in said intake passage;
• e) calculating the amount of change in the intake pressure between at time when opening said exhaust gas recirculation valve and when closing said exhaust gas recirculation valve while in a fuel-cut operation where the fuel supply to said engine is interrupted;
• and
• f) determining the abnormality of said exhaust gas recirculation mechanism according to the amount of change in said intake pressure;
• wherein said engine is controlled by using said at least one control parameter suitable for a closed condition of said exhaust gas recirculation valve during a predetermined time period from the time of first opening of said exhaust gas recirculation valve after finishing the abnormality determination.