2001 Oldsmobile Alero Engine Size : 2.4
Question : My car seems to idle high between shifts, the rpm doesn't seem to drop as fast as it should. What could be the issue?
Answer: Usually a high idle is due to a small vacuum leak or driveability problem. By your description this sounds like you are talking about going from park to drive or reverse, not the transmission shifting when driving, you're just noticing it mostly between shifts. You need to get the car scanned and see if there are any trouble codes. Plus a technician can watch a live data display and see if there any trouble area that are causing the high idle.
Sometimes it can be a bad throttle position sensor, idle air control valve, or even a bad computer. There are quite a few things to check, but you can start off just by making sure the air cleaner is installed correctly, and the ducting from the air cleaner to the throttle body is all connected right. Check vacuum hoses, brake booster hose, etc, to see if there are any leaks. Usually you'll hear a hissing type noise where air is being sucked in.