an idle condition or the vehicle is put in a normal running condition in this manner typically engine 1 is automatically stopped when the vehicle stops at a crossing in the street or the like and automatically restarted at start of the vehicle on the other hand if it is determined in step s 7 that engine stall that was not intended by the driver was caused the program proceeds to step s 8 where it is determined whether the system is in a fail mode i e whether it is determined whether engine stall has resulted from forced stoppage of engine 1 due to the fail mode engine control module 10 monitors the whole control systems of engine 1 at all times so as to determine whether there is caused something abnormal e g if it is determined that there has been caused something abnormal such as extraordinary rise of the water temperature extraordinary rise of the oil temperature and some sensor trouble engine control module 10 causes the control mode of the whole control systems to be transferred to a predetermined fail mode and may forcedly stop engine 1 depending upon the kind of abnormality in such a case it is not desirable to automatically restart engine 1 thus the program proceeds to step s 11 to wait for the fail mode to be canceled in the meantime under this condition it is also desirable to make it impossible to attain even manual restart of engine 1 by ignition key switch 9 in case the fail mode is caused by extraordinary rise of the water temperature or the oil temperature the lapse of time may cause the fail mode to be canceled and the control mode to return to.