IAC help

[MelectroK]

My car has a horsepower surge now at constant throttle notice mostly on the hightway. From what I can gather, ether it sound I need to replace my IAC or remove it to clean the passage.

What excatly is the IAC and how exactly does it work?

 

[Rockledge]

Generally, the Idle Air Bypass Valve/Solenoid is one method that Ford uses to control the RPM at which your engine idles. When you the driver are not demanding a given engine RPM, the ECM takes control and establishes correct RPM based on engine load and temperature. Consistent with that, it prevents the engine from stalling when you let up on the gas (closed throttle/deceleration) and is also partuclarly important at startup.

An IAB consists of a coil type solenoid directly connected to a valve with a return spring. When no voltage is applied to the coil, the valve is closed. When voltage is applied the valve is fully opened. By using a process called "pulse width modulation", the valve can be partially opened. More on the IAB can be found here:

http://fordfuelinjection.com/iab.html

From what you describe, I agree that it's probably worth taking a closer look at your IAB:

http://www.shotimes.com/SHO3surge.html

http://www.shotimes.com/SHO3iabclean.html