Sounds likely. Both answers sound likely. I've got nothing to lose but time by trying to unplug the idle circuit.
There is a passage in the GMC maintenance manual under "Cleaning and Inspection" of the downdraft carburetor that states:
"...Be sure all carbon deposits have been removed from throttle bore and idle port. It is advisable to reverse the flow of compressed air in all passages to insure that all dirt has been removed...CAUTION: Never use a wire or drill to clean out jets."
I'd better use a small wire as a last resort. The diagram of the idling system in the shop manual has some sharp turns in it and some of it seems completely unreachable by means of a wire.
1946 Chevy pickup, 1948 Chevy suburban, 1950 Chevy pickup, 1952 GMC pickup, 1957 Chevy pickup, 1939 Chevy pickup
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