A good scanner will give you real time temperature readings. That sensor is not in a real fun spot. Hopefully, if it is an injector, it's just dirty. Something a bottle or two of Techron may fix. On a car I had with CIS injection the injectors were ruined by cheap gas and gas watered down with alcohol. They would leak a drop or 2 and the car was real hard to restart. Only way to test was to remove the injector system from the intake, stick them in a jar or bucket and pressurize the fuel rail. If it weeps gas swap them out. I would run cleaner through them first...
While you have them out replace all the o-rings and the gaskets. Especially the ones under the fuel rail.
