Idle too fast when hot. Air idle control valve?SIDLE

Have just changed head gasket. All seems OK except engine idles hot at 1500rpm. I suspect AICV. I removed the hose to AIVC ahead of throttle, enine ran normally. I then blocked this pipe and engine immediately stopped, suggesting no leaks anywhere else. Do these AICVs respond well to cleaning, or should I replace? Could it be anything else, e.g. coolant temperature sensor?

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