Ok this is what happens when I start it it revs to 2000 and stays there until it warms up then is fine. But if I drive it before it warms up it surges up and down. There is no CEL and it drives great I am trying to sell it and need to know what it could be

 

fast idle valve. located under the throttl body, has a collant line going to it

 

what do I do to it

 

Check the coolant level in the radiator first.

 

the reservore is empty does that matter

 

Check the level in the radiator. Top off the radiator and the overflow tank. If this solves your driveability issue, don't forget to fix where you have a coolant leak also.