[Mgs] MGA high idle

[W. David Houser]

List,
Friend has been having some probs. lately with her MGA. Latest came  
overnite when she started it up. It idles up to about 3000 rpm and  
wouldn't come down preventing her from driving it to a car show.
It has driven well prior to this and has a generic "Weber" carb in  
place of the SU's. I can't help her with that.
Is anyone with a Weber type carb able to offer me any ideas on what to  
look for and hopefully fix?
TIA,
Dave Houser