Hi,
That is a typical symptom of the throttle position sensor. Get a digital voltmeter and connect to the black and orange[green on some years]wires, turn key on,engine off. meter should read DC volts. 0.997 is optimal setting, yours probably reads 0.8xx something. loosen the 2 black screws and try and move the sensor to give that voltage reading. If not enough adjustment,then take it off and use a small round file or drill bit and make the holes 'slightly' bigger and try again for 0.997 volts, don't adjust over 1 volt. If the idle still varies ,the carbon in the sensor is breaking down, get a new sensor.
Perry.
