As mentioned, check the vacuum hoses. You might have knocked something loose while changing the oil filter.

If the ACC vents work, I mean anything but defrost, and you can't shut off the engine with the ACC system off then the problem probably not a vacuum leak in the ACC system.

Look for the red line with a green stripe going into the cabin in the area of the brake master cylinder. Cap that line on the engine side and you've isolated the ACC system from the engine vacuum system.

Sixto
91 300SE
87 300SDL
83 300SD