how to test it?

i have a Renault Clio auto car that can sometimes race on start up and can go up to 3 thou revs and sit there the only way to stop this is turn the ign off,and try it again this may happen 2 or 3 times before the car starts up normally as if nothing had happened have also had it speed happen going along the road after losing foot off pedal the throttle cable has free play in it
how do I check/setup even TEST? a idle speed control actuator

dave
January 2011