General Maintenance & Repairs - IAC Problem

I removed the IAC to clean it and to make sure it was working. When i turned the key to the on position to see if it would move the threaded shaft unscrewed itself and popped off the valve, spring and all. I put the spring and shaft back into the valve and turned the key on, it then threaded itself back in. So i bolted it back on but when i started the car it would stall right away. I removed the valve again held it in my hand, while the key was turned on then off. The shaft moved up and down. I bolted it again and the car started normally but when i turn the car off while touching the IAC i can feel a vibration like it the shaft wants to move but it can't, then stops (almost like motor spins but the shaft can't go anymore). Do i need a new IAC ?