Idle should be 750+/-50 -Big_Benz- ♂   (638 bytes) (36 reads) 2004-10-29 

when you have your transmission in P.

All cars will have a high idle for the first 5 second or less at 1200 - 1500 RPM. It will depend on the outside Temp as how long it takes to go down.

If your car stays at 1500 to 2000, you got a problem. High idle like yours will damage your transmission, wear out your brake, and use more gas.

My old MB has a very complicated idle control system and I have studied the issue for 6 monthes. At the end, even dealer coul dnot find out the root cause but I solved it DIY. Let me know your make, model and year. I could suggest a long list of step by step to diagnostic.

http://web.wenxuecity.com/BBSView.php?SubID=auto&MsgID=122227