[MaSnaka]

Had a similar problem. Not so much from heat or a hot day. Come to a stop light or stop sign and the RPMs would hang up and a soft tap on the throttle would return to normal idle. I thought the advance timing in the dist. were sticking so cleaned and lubed with wd4o, didn't solve the issue. Found the lower throttle plate of the carb was worn at the shafts that control the butterflies. A little bit of play was allowing air to enter below the butterflies or maybe not allowing the carb to settle all the way back to idle. So I replaced the throttle plate and problem is solved. The carb has some miles maybe 30K and 15 years old. 2 springs. I hope this helps. Good luck.

John