1998 VOLVO S70 T5 Exhaust black smoke

[LEEGary]

I was away from home for a month and a half due to work, leaving my Volvo S70 in my father's care. I instructed him to frequently start the car and drive it a certain distance because the previous owner had installed an aftermarket anti-theft device, and the car is prone to power loss if the battery isn't charged regularly. However, he completely neglected to take care of my car. Anyway, today I bought a new battery and installed it. The car starts, but there's thick black smoke from the exhaust pipe, and a gunk smell. The idle speed seems okay. I did a quick check, unplugging the ICV connector, and the black smoke disappeared! I'd like to ask if this indicates the ICV is completely broken, and what the possible causes of the malfunction are?
Thank you for any replies!

[abscate]

They rarely break, they can get stuck though. I would take it off and clean it out with throttle body cleaner