Hi JimBlake, I'm going to check the pivot shaft and report back. It's weird because if I recall correctly, it happened last year too around the same time of year and NYC heatwave. I thought it might be some throttle control sensor if that even exist.

 

I don't think there's any kind of thing that's SUPPOSED to hold open the throttle. Motorized throttle comes a year or 2 later than your car.

Work the throttle and the cable drum, see how all that stuff works with the engine turned off. If you can figure out what's preventing it from closing all the way, then you can fix that.