I have been trying to adjust my idle speed up a bit to reduce vibration. I am not sure where the device is that boosts idle speed when the transmission is in drive, but it appears to be malfunctioning. The idle speed runs about 900-1,000 in park, but around 600-700 in drive. I need it a bit higher in drive so I either need to get it higher in park, or replace whatver part has gone bad that is allowing the speed to drop. I have had this car since it was new so I know that it used to auto-adjust. Any time I adjust the speed up with the screw on the throttle body the car seems to "self-adjust" it back down.