there isn't an idle control valve.
Whoever said that probably means the aux air valve which is located underneath the inlet manifold, bolted to the water pipe. It's job is to increase air flow and idle when the engine is cold, when it's up to temp it's supposed to close. It's a simple valve controlled by a bi-metallic strip which loses it's springyness over the years. If they stick then they can cause idle problems by effectively creating an air leak. I don't think you can buy them new any more and 2nd hand ones aren't likely to be much better. I had some limited success taking it off and soaking it in carb cleaner for a while to clean it out.
Other than this, check for any air leaks - worn out vacuum pipes, throttle body gasket etc...
Also check the ignition timing using a timing light.