[POORSH]

Don't know exactly to put this thread, but here goes. I just picked an '86 Mercedes 190E 2.3 16V at what I think is a pretty good price from a friend. I've always admired these cars (being a child of the '80s) along with the E30 M3. This one just kind of fell into my ownership. It is a one owner car with 80k original miles. While it is a nice car, it has one big problem and a couple of small problems.
BIG problem: it will pass smog at 25 mph, but not at 15 mph.
small problems: A) needs a/c compressor and if the vac system is turned pass the first notch, a fuse will blow.
B) the driver's door lock doesn't work. I have to open/close the drivers door via the trunk or passenger's door.

The big question is what would fail it at 15 but pass it at 25?

Any input will be greatly appreciated.
Thanks in advance.