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.

PS.
Let us know which solution worked for you.

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
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