Idle surge is not caused exclusively by the Idle Control Valve.
Other causes of idle surge are:
1.- Vacuum Leaks (the hoses that connect to ICV, Intake Manifold Gasket, etc..)
2.- Air Mass Potentiometer wore out (there are excellent posts with pics.... do a search)
There are many solutions already posted, most likely one of those will solve your problem.
Good Luck and keep us posted.
Let us know which solution worked for you.
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car