Don't know if the valve is supposed to be clicking, never had it happen.
I had a real idle control and rough idle problem on my '89 560 . I decided to clean the valve using brake cleaner - took forever, but was kind of fun, whatching all the gunk come out.
I then lubed the valve using sillicone lube spray. These were all Moedips ideas (senior member to this board).
My idle problems are gone...
