If it was shifting okay before, then I would inspect the lines that you hooked up for being plugged or damaged in some way. Are you sure they are in the correct position?
Next, when you installed the IAC, did you make sure it wasn't extended too far before installation? I have attached that below. Then you need to make sure you reset it so the PCM can reset.
INSTALL OR CONNECT
NOTE : Before installing a new idle air control valve, measure the distance that the valve is extended. The measurement should be made from the idle air control valve motor housing to end of the idle air control valve cone. The distance should be no greater than 28 mm (1-1/8 in.). If the idle air control valve cone is extended too far, adjustment is required, otherwise, damage may occur when the idle air control valve is installed. Adjust the idle air control valve by manually compressing the pintle to achieve the correct length.
1. Install the new idle air control O-Ring.
2. Install the idle air control valve in the intake manifold.
3. Install the idle air control valve (2) attaching screws.
" Tighten the idle air control valve attaching screws to 3 Nm (27 lb. In.).
4. Install the electrical connector to the idle air control valve.
5. The PCM will reset the idle air control valve whenever the ignition switch is turned ON, then OFF. Turn the ignition switch ON, then OFF.
6. Start the engine and allow the engine to reach operating temperature.
For no shift the info states a possible control valve problem, stuck or binding 1-2 shift valve. But again, if it was working okay before the IAC change, that is where I would start and make sure all is hooked up okay, vacuums and connectors. Reset the PCM.
Next, I would do what I could to go to Auto Zone (AZ) or O'Reilly's (OR) and for FREE they can pull the codes to the car. Most important: Once they check your codes, if they find something and you don't get it fixed and need to get back with us, please make sure you tell us exactly what the code was, number and all. Example, if the code was E0568 O2 Sensor bad. Then make sure you give us all of that. While there for FREE also they can bring their tester out and check your battery and alternator.
With the codes we may be able to narrow it down more.
Saturday, January 17th, 2009 AT 11:40 AM