The most common problem is the IAC valve (idle air control)
The Idle Air Control (IAC) valve adjusts the engine idle speed. The valve is located on the side of the throttle body. The valve is controlled by a duty cycle signal from the PCM and allows air to bypass the throttle plate in order to maintain the proper idle speed.
The IAC is located at the top of the upper intake manifold adjacent to the throttle body.
Do not attempt to clean the IAC valve. Carburetor tune
-up cleaners or any type of solvent cleaners will damage the internal components of the valve.
See Figure 1
Fig. 1: The IAC can be monitored with an appropriate and Data-stream capable scan tool
Turn the ignition switch to the OFF position.
Disconnect the wiring harness from the IAC valve.
Measure the resistance between the terminals of the valve.
Due to the diode in the solenoid, place the ohmmeter positive lead on theVPWR terminal and the negative lead on the ISC terminal.
Resistance should be 6-13 ohms.
If resistance is not within specification, the valve may be faulty.
REMOVAL & INSTALLATION
See Figures 2, 3, 4 and 5
Fig. 2: Unplug the connector from the IAC valve
Fig. 3: Remove the two retaining bolts and ...
Fig. 4: ... lift the IAC valve off of the intake manifold
Fig. 5: The gasket must be replaced for the IAC valve or an air leak could occur possibly causing driveability problems
Disconnect the negative battery cable.
If your vehicle is equipped with the 2.0L engine, raise and support the vehicle.
Disconnnect the wiring harness from the IAC valve.
Remove the two retaining bolts.
Remove the IAC valve and discard the old gasket.
Clean the gasket mating surfaces thoroughly.
Using a new gasket, position the IAC valve on the throttle body.
Install and tighten the retaining bolts to 71-106 inch lbs. (8-12 Nm).
Connect the wiring harness to the IAC valve.
If raised, lower the vehicle.
Connect the negative battery cable.
It should be tested and replaced if not funstioning properly.
If you have further questions on this just reply.
Thanks for asking!