Andy, I would adjust the lower idle screw when the car is warm, Only because when it's cold the idle speed motor air passage should be open. So: when the car is warm, adjust the lower screw to the idle you desire ( mine by the tack is 850-900 ) then adjust the upper screw to actuate the switch, you should hear it click when you turn the screw in. There is a picture on the site and this info in other words is in the technical manual, if still not right, then you would have to trouble shoot for motor problems, air leak, or bad thermister. Hope this helps John Hervey http://www.specialtauto.com/ref_main.shtml