A four cylinder Camry car, the fault is idling imbalance, high and low, and sometimes also put out the car. The first response is that there is a problem with the idling system, and it is very likely that the idle valve is removed and the idle valve is removed for cleaning. However, the idle speed is still unstable. When the idle valve is identified, the throttle body is cleaned. After suspicions EGR closed is not strict, then changed a EGR, after the idle speed after the fault cleared, two days after the same failure again, through the connection TOYOTA diagnostic apparatus to check engine data? It is found that the water temperature signal is abnormal? Change the water temperature sensor, failure no longer appear.