Does your car idle rough or the speed cycle up and down. You probably have a bad idle air control valve. The only purpose of the idle air control valve is to keep the engine’s idle smooth. The engine’s computer gives the idle air control valve the feedback it needs to hold a constant rpm. The idle will be around 1000 rpm’s when not in gear and around 800 rpm’s in gear. This iac valve is on a Nissan Maxima and is similar to most idle air control valves.
As you can see in this picture there are channels running inside the valve. The iac is a valve with a taper on the end of it that moves in and out to control the air past the throttle into the engine. The air controls the engine speed. This paticular valve also combines a channel for coolant to pass through to help heat the throttle body air. To remove the throttle body you will first need to remove the airbox screws. The have an arrow pointed at them.
Remove the top two cables from the clips on top of the airbox. Then you will need to remove the coupling that fits between the airbox and the throttle body. The two clamps shown here will need to be loosened.
You will need to move around the airbox to remove the coupling. Next you will need to remove four bolts that hold the throttle body on.
Once the bolts are removed there are three electrical plugs that will need to be removed. One is located underneath and is difficult to get at and the other two are on the left side. As you can see in this picture, the green tab will need to be pushed in and up to release the plug.
Rotate the throttle body to the right and rotate the throttle until there is enough slack in the cable to slide it out of the hole. Both will need to be removed. Then there are two hoses that will need to be removed, then you can finally remove the throttle body. Look on the bottom of the throttle body to see the idle air control valve.
To remove the idle air control valve, simply remove the five screws that attach it to the throttle body. If you also left the hose on the iac valve, as is done in this picture, don’t forget to attach it to the new idle air control valve. Then reassemble everything opposite the way you removed it.