In the Morning the engine start up and then stalls immediately

Hi, after changing the radiator as it was rusty and in bad condition and caused the engine to run in a higher temperature, now in the morning the engine starts up normally and directly stalls. I have to put my foot on the pedal to make the rpm up to 1000 for five minutes at least. I went to reputable mechanics he checked the throttle body and the sensors attached and found one sensor was blocked with the contamination. He make the necessary repair and also changed the spark plug, the fuel filter, the air filter and checked both the pump pressure, the injectors and temperature sensor and it is okay.
Also, the engine fuel consumption is too high.
Thanks for your assistance.