Well...cars are built to withstand idling with no air flow, excluding thermal fans, for hours on end without overheating or stalling due to heat. If your temp guage isn't through the roof, than i doubt it would be a heat issue. There's heaps of post up about stopping at lights stalling, so have a quick search. Most common being an atmo bov, aac valve issue, etc. You get the picture. Good luck.