The recent very warm weather has high-lighted a niggle with my car; once the engine is fully warmed up the car idles at a noticeably lower speed than if the ambient temperature is a lot cooler. On coldish days it doesn't happen, only on warm days........ Any ideas what may cause this? I'm guessing possibly a sensor? All gauges etc read OK and car goes like a bomb, just a bit irritating to have car idling far too slowly at traffic lights etc , its the same irrespective of whether the aircon is switched on or off too....... Thanks!