THE IDLE IS SUPPOSED TO BE MODESTLY HIGHER IN NEUTRAL OR PARK. THE IDLE CONTROL IS CONNECTED TO THE NEUTRAL SAFTY SWITCH FOR THIS INPUT.
SINCE THIS CAR IS AN AUTOMATIC THE TACH. IS REALLY FOR ENTERTAINMENT,HAVE YOUR TACH. CHECKED AGAINST AN ELECTRONIC SHOP TACH. AND YOU WILL FIND THEY ARE OFF BY 100RPM OR MORE(TYPICAL)
MF