If I read your question correctly you are asking what makes the engine idle high until it reaches full temp. The computer runs in open loop when the car is cold to speed up the warm up process and to reduce emissions the computer makes the engine go to fast idle. When the engine reaches a certain temp the computer goes to closed loop and slows the idle and begins to take more input from the engine sensors . When the car is in open loop such as when cold this is the equivilent to when the car is fully warmed up and you floor the throttle because at this point the car also goes from closed loop to open loop for maximum performance. I hope I read your question right you may already know this info.
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