I own a 1999 Ford F-150. My mechanic says I need to replace the Idle control air valve. What does this valve?

do and what does a defective one do to my idle speed and rpms? The motor is a 4.2 litre V6. Thanks, CurtI own a 1999 Ford F-150. My mechanic says I need to replace the Idle control air valve. What does this valve?
This is a computer controlled, electronic stepper motor that is used to control the idle speed. There is a target idle speed in the powertrain control module and it uses this motor to control the size of an orifice that bypasses air around the throttle plate. Increasing the amount of air (opening the valve), will increase the idle speed, while decreasing the amount of air (closing the valve), will decrease the idle speed. The PCM uses various sensor inputs to tell how fast the air is going, as well as to tell if the air/fuel mixture ratio is correct. A defective valve can have several symptoms. If it is stuck open, then it can cause a high idle or dying problem, if stuck closed it can cause low idle or for the vehicle to die. If it is slow to respond it can cause and idle hunting condition, like when it goes up and down. If it gets stuck in a certain position it can cause erratic idling. The valve also opens and closes, even when accelerating, decelerating and cruising to make the changes more smooth, and it can have performance affects even above idle.I own a 1999 Ford F-150. My mechanic says I need to replace the Idle control air valve. What does this valve?
The idle air motor does just that!It controls the idle. A bad one could cause stalling or erratic idle
The Idle Air Control valve (IAC) controls the engine idle speed. The output actuator is mounted on the throttle body and is controlled by voltage pulses sent from the PCM (computer). The IAC valve pintle moves in and out allowing more or less intake air into the system according to the engine conditions. To increase idle speed, the PCM retracts the IAC valve pintle away from the seat and allows more air to bypass the throttle bore. To decreaseidle speed, the PCM extends the IAC valve pintle towards the seat, reducing the air flow. To check the IAC valve unplug the electrical connector and, using an ohmmeter, measure the resistance across terinals A ans B, then terminals C and D. Each resistance check should indicate 40 to 80 ohms. A bad IAC will cause the engine to run rough, stall, hard to start. The engine can die when driving and make you mad enough to slap your moma. It can be dangerous to drive.
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the idle control air valve main job/func you can noticed is when starting the engine in the morning.. did you noticed the idling of your car is a bit high? after 1-2minutes it all came to normal idling rev.. and when turning on the air-condition.. theres a slightly change in the RPMs.. why? its simple the idle control valve make sure your engine turn on.. rather than stepping on the gas pedal all the time
Its your air sensor for whats coming into the car, its something you can change yourself.
This is a common problem on Ford V8s.. The good news is that it is simple and cheap to replace. It is a small electric air control valve that is attached to your throttle body. It lets a regulated amount of air flow behind the closed butterfly when the throttle is closed so the truck can idle. When they get stuck you idle rough or the truck is hard to start or keep running at idle.. I think the part is about $60 US and you can just bolt on a new one in 15 minutes.. Hope this helps.