It could be the fast idle valve, but since that is temperature controlled I'd bleed the cooling system first. On the upper coolant neck you'll see a bleed bolt (kinda looks like a grease fitting). Crack that open and bring the engine up to operating temp. When no more bubbles come out your done.

The fast idle valve is on the back of the intake and a b!tch to get at. Suggest investing in a Helms manual.