I have found the high idle problem to be worse during warm weather, but I think all you have to do is put a restriction in the supply line to the IAC valve. As a test, squeeze the hose with a pair of pliers, and you'll see the idle will drop and hold the proper level. There is a description of the fix on this website. I used a laboratory clamp on the outside of the hose. This type of clamp can be adjusted as required.
Marvin Stockman
