Of Mitsubishi variant, the ISC (Idle Speed Control) servo valve need to be cleaned especially the secondary gear support shaft. This support shaft is basically a hollow sleeve that accepts the secondary gear which will turn according to the engine load demand by opening the bypass air passage from below the throttle body to allow more air into the throttle body which will raise the rpm especially during idling where the vacuum is greatest. These transfer gear may crack as they are made of plastic and if true will need to be replaced.
