Cold start problem

My car has a 4.6L V8. Lately, when it is started cold, it fires right up but stalls immediately unless you keep your foot on the gas pedal 9it is starved for gas). When I took it to the mechanic, he was unable to duplicate the problem (it works normally after the car has been at operating temperature for a period of time. The car has been tuned up and and engine cleaner and gas line water remover have been used with no effect. My guess is that either a sensor is malfunctioning or there is a problem with the emission control equipment. If you have dealt with this type of problem and fixed it, please give me some advice on where to look for the problem.

The problem might be caused from a defective Idle Air Control motor.

The IAC motor is what controls the engine idle under all conditions by controlling the amount of air that enters the engine. If the IAC motor fails to go to the proper position for the idle condition the engine stalls due to the lack of air entering the engine. When you step on the accelerator when this happens, the throttle plate opens slightly allowing air into the engine that the IAC motor isn’t, and this prevents the engine from stalling.

Tester

Check the temp sensor. The idle air would cause surges or stalling after the car is warm as well. The car may not be getting a cold start rich mix.