Reset 86 Camaro Idle

I have a 86 Camaro that has been sitting for about 3 years without being started. So i went out bought a new battery and installed it. I started the car right up it ran at a high idle of 2500rpm but after about 10 min when the temp came up i kicked it down and it stalled right out. I restarted the car but this time i had to keep my foot on the gas and keep the idle above 1000 rpm or the car will/would stall. I called a dealer and they said i have to have it "RE LEARN THE IDLE SPEED" so i read a article that said "Just drive it for 20 min and it will relearn the idle speed" so that's what i did. I ran it down the hi way for 20 min and still the same problem is going on. SOMEONE please tell me how to fix this problem...