Ford pick up idles up and down by its self ?

This problem is noticed by many users.This is due to problem with idle air control valve.
The idle valve needs to be inspected ,tested and replaced.

Idle Air Control Valve (IAC)

OPERATION

The idle air control valve (IAC) control the engine idle speed and dashpot functions. The valve is located on the throttle body on. This valve allows air to bypass the throttle plate. The amount of air is determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal.

TESTING

1. Make sure the ignition key is OFF .
2. Disconnect the air control valve.
3. Use an ohmmeter to measure the resistance between the terminals of the valve solenoid.

Due to the diode in the solenoid, place the ohmmeter positive lead on the VPWR pin and the negative lead on the ISC pin.

4. If the resistance is not 7-13 ohms replace the air control valve.

REMOVAL & INSTALLATION

See Figures 1, 2, 3 and 4

Fig. Fig. 1: Unplug the connector at the IAC valve

Fig. Fig. 2: Remove the two screws retaining the IAC valve

Fig. Fig. 3: Remove the detached IAC valve from the throttle body

Fig. Fig. 4: Remove the gasket from the throttle body

1. Disconnect the negative battery cable.
2. Disconnect the engine wiring to the IAC sensor.
3. Remove the two retaining screws for the valve.
4. Remove the IAC valve and discard of the old gasket.

To install:

5. Clean the area of old gasket material.
6. Using a new gasket, attach the IAC valve to the engine. Tighten the retaining screws to 71-102 inch lbs. (8-12 Nm).
7. Connect the IAC valve wiring to the unit.
8. Connect the negative battery cable.

The above mentioned detail will help you to confirm the problem and replace the IAC ( idle air control valve).