Originally Posted by Dave McB
yeah it can actually run fine without one.
All u need to do til u fix it or whatever is unplug it and adjust the idle screw (under the throttle body) to the right idle setting
... and this is probably the problem, base idle adjustment not right, that is causing the fluctuations...
With the engine at normal operating temperature, unplug the idle valve and adjust the idle speed (screw in bottom of throttle body) to 850-900 rpm.
When you connect and disconnect the idle valve there should be no change in rpm, readjust if necessary.
If base idle is set below nominal idle speed of 850-900rpm, the idle speed valve will struggle to maintain smooth idle, and you will get fluctuation..