Toyota Pickup

Just bought a 1985 Toyota Pickup with 138k miles. The idle is really low and erratic when it's in drive and goes high when in park. There's a bit of black smoke that's coming out of the exhaust too. Also, it isn't getting the best gas mileage. Quite sure that it's the carburetor but not sure if it needs an overhaul or just an adjustment, and don't know how to do it either.
Any help would be greatly appreciated, thanks.
May 18, 2006.

With an older truck with the 22R engine, I would do a complete old style tune up. A black exhaust means you are running rich. Check all the vacuum lines and make sure they are OK. Look at the side of the carb and see how the fuel level is in the window. It should split it. They were famous for having bad timing chains and tensioners. Let me know.

May 20, 2006.