Toyota Repair: Stalling at idle, air control valve, fuel injection system

Question
My 99 Toy Camry has begun to stall at stop signs, at idle. It seems that when the RPM needle goes below 1, the engine knocks and shuts off. I also notice that the temperature gage seems stuck at cool even 15-20 minutes after start. Are the two related? I took it to a shop and they couldn't get the car to duplicate the symptoms, so they cleaned the fuel injection system.I'm frustrated. Help!
thank you

Answer
The engine has to come to operating temperature so the computer can control the engine functions, if it doesn't I would recommend replacing the thermostat first and then see if there is an improvement.
If that shop couldn't duplicate the condition they should not have made a repair attempt by cleaning the fuel injectors, it obviously wasted your money so I would not go back there.
Camrys are known to have idle control problems so if after replacing the thermostat and the engine gets to normal temperature the idle problem still persists replace the idle speed control valve.(Sometimes called idle air control valve).