Special thanks to Sven Pruett from Vanir Technologies for this write-up
4.0L Ford V-6 Idle Speed Setting Procedure
In some cases, the installation of a larger throttle body will result in an idle speed that is slightly higher than normal. If this condition occurs, the base idle setting will need to be re-set according to the following procedure. NOTE: Engine should be at normal operating temperature before performing this procedure!
1) Turn off all accessories & disconnect the battery for 5 minutes.
2) Reconnect battery. Disconnect the Idle Speed Control (ISC) solenoid located just behind the throttle body on the drivers side of the upper intake plenum.
3) With the truck in NEUTRAL, run the engine at 2500 rpm for 30 seconds.
4) Let the engine idle for 2 minutes.
5) Put the truck in PARK (or NEUTRAL if manual trans.) and adjust the idle speed stop screw until the idle is at 700rpm.
6) Turn engine off and let sit for 2 minutes then repeat steps 1-5 once.
7) Disconnect battery for 5 minutes then reconnect.
8) Reconnect the Idle Speed Control (ISC) solenoid.
9) Run the engine at idle for 2 minutes.
10) Quickly depress the accelerator pedal to the floor and release it immediately, allowing the engine to return to idle.
11) Lightly depress and release the accelerator allowing the engine to return to idle.
After carefully following the above steps, the engine should now have reset its base idle to factory specifications. The idle should now be smooth and at approximately 700rpm at operating temperature. If this procedure does not correct the fast idle condition, carefully check for vacuum leaks at the throttle body flange gasket and at the intake snorkel to throttle body interface. If no vacuum leaks are detected and the condition still exists, a condition that is unrelated to the mechanical throttle body assembly exists and must be diagnosed and repaired.
