Intake air flow control system for internal combustion engine

To provide an intake air flow control system for an internal combustion engine with which it is possible to prevent a rise in cost and to prevent adverse effects on the starting characteristics of the internal combustion engine. At the time of performing a reference position adjustment of an auxiliary intake air flow control valve, when both a first re-reading condition where the absolute value of the difference between a target idling engine speed and a current idling engine speed is smaller than a first threshold and a second re-reading condition where the absolute value of the difference between a calculated intake flow rate and a reference intake flow rate is greater than a second threshold are established, step S5 is performed in which a valve opening corresponding to the reference intake flow rate on a reference characteristic basis is used in place of a valve opening corresponding to the calculated intake flow rate.