CONTROL METHOD OF INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To solve the problem wherein the possibility of causing preignition becomes high even in a combustion cycle after automatic starting when the preignition is caused in a combustion cycle before automatic stopping, and the preignition is caused in the first several explosions after the automatic starting in such a state that the automatic stopping time by an idle reduction is short and the automatic stopping is frequently repeated without sufficiently cooling an internal combustion engine in an automatic stopping time, in a control method of the internal combustion engine having idle reduction control for automatically stopping the internal combustion engine when a predetermined stopping condition is established and automatically restarting the internal combustion engine when a predetermined restarting condition is established.SOLUTION: Whether or not preignition is caused in an internal combustion engine 10 is determined from an ion current detected by an ion current detecting device 30, and the occurrence of the preignition in a combustion cycle after restarting of the internal combustion engine 10 is avoided when the preignition is caused in the combustion cycle before stopping the internal combustion engine 10.