how do you adjust the throttle body carb it seems to be too rich and fouling plugs

 

Is your van throttle body injection (TBI)? If not sure then pull off the air cleaner top and look down at the throttle body if you see electrical wires and two things pointed down (the injectors) towards the throttle plate then it is TBI and if so then a couple of probable causes would be a failed O2 sensor or failed fuel pressure regulator. There is not adjustment on the TBI except maybe the idle stop.

 

All right, I'm getting spooked by the number of 1989 vans with issues.

Unless someone replaced the TB with a carb, there is no user adjustment. The Computer varies the mixture according to inputs from the Coolant temp sensor(2 wire), the O2 sensor, and the TB charge temp sensor and possibly some other factors as well.

If you air filter is extremely dirty, it can also cause rich running.

Now if a cylinder is not firing for whatever reason, the exhaust will smell rich.

Do a key dance, post any codes, and a basic tune up. New distributor cap with copper or bronze contacts, not aluminum. New spark plugs and wires.

Put a can of seafoam in the tank.

There should be a sticky on how to do a key dance and how each new thread should have any codes posted, but a search will reveal the procedure.

 

Just like in the movie "Terminator" where each and every Sarah Conner was eliminated until the correct one was found...the Gremlins are coming for you. Be afraid...be very afraid.