[TR] Sudden change in idle

[terryrs at comcast.net]

TR3A runs throaty and smooth and driving speeds, with power to spare.  But since yesterday when I come to a stop, the idle drops to about 500 rpm, keeps it about a minute, and then dies altogether.  
Timing of this does seem to coincide with a recent heat wave in the Northeast, where we've been having 90 degree weather.  (At least I'm convinced all the snow is now gone....)
Has electronic ignition.  No smell of fuel.  Did a recent valve adjustment...may have gotten them a bit tighter than I should since I measured them to .10 at warm instead of cold.
Suspect fuel.  Sounds like one of the carbs is off.  Will look to see if the choke hung up on one of them.
Any ideas where to start?
Terry Smith, '59 TR3A
New Hampshire