blb

My '94 22RE starts right up, idles fine until right after the thermostat opens up, then the idles surges up and down. (I understand it is the computer that tries to bring the idle down}. After it is fully warmed up, the surging goes away and it will idle fine as long as it stays hot. The temperature gage reads normally. So far, I have replaced the radiator cap, replaced the thermostat, lowered the idle speed to 700RPM, checked all vacuum lines, and elevated the front of the truck while it was running to try to get any trapped air out of the cooling system. It still does the same thing. The surging idle only occurs right after the thermostat opens up and it stops surging after it is fully warmed up. What am I missing? Any ideas to get rid of this problem will be greatly appreciated.