94 E250 Blowing Smoke

Van runs rough, whether cold or hot and lacks some power, also blows black smoke. I checked the codes...rich on right side, so i changed the oxygen sensor...no change in performance. So i changed the plugs (which were covered in black soot), wires, cap and rotor...no change in performance. I dont have any other codes, any advice is greatly appreciated. (123,00 miles)

I just learned about the IAC-idle air control- valve. It's located on the top of the throttle body(4.9 engine 1993). there are two bolts that hold it on. One on either side. From inside the van, take off the doghouse cover. Then remove the electrical connection on end of the IAC. You'll see the IAC just above the two air intake ports on the throttle body. the first bolt is easier to get from the inside, the second one is easier from the outside after you remove the air cleaner and set it to the side. Once removed, you can use an auto parts cleaner to remove any build up inside the IAC ( I used Q-tips). There are two types of IAC valves, one is cleanable the other isn't. The cleanable one has two holes on the bottom where you can see the inside of the IAC. the other on , you can't see inside. If you have the second one, you'll have to replace it. Good luck, I hope this helps. P.S. you may want to pick up a repair manual specific to your van, they are really helpful!