By-Pass Air Control (BAC) Valve
WARNING: This page is about a different car, the 1997 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
BAC valve is located under throttle body. Remove BAC valve. Circulate cold water in BAC valve coolant input hose to cool valve. Circulate hot water in BAC valve coolant input hose and ensure air valve operates. Replace BAC valve as necessary.