Oops Lomac, I misread your post.. if it is a 94.. you can read the codes by the pedal
OBD1 Pedal trick
then it is OBD1.
Fault problems: Well display on the OBC might become delaminated, some finger pressure will fix it temporarily. Check aircare history to see what kind of emission readings it might be.. since a bit rich can do bad things to the cat. But e36 is a simple car, buy a spare expansion tank just in case?
Run the ad, by the armchair shoppers on BCBimmers.. chances are someone would have looked at it beforehand.