There is a very loud rattling sound that comes from the exhaust/muffler when my car is on and I stop (put the car in idle). It doesn’t happen every time, but if my AC is on, and I’ve just stopped the car at a light or stopped the car while parking/backing out of a parking space, the noise is very likely to occur (more than 50% of the time). The noise often temporarily goes away after 5 seconds or so when stopped. If I idle forward a few feet and hit the breaks again, the noise will usually start up again. The noise never occurs while accelerating.
The AC also seems to work well. Although I once had trouble getting up a mild hill with the pedal all the way floored.
Two mechanics have looked at the car. One did not find anything. The other found minor scorching in the spark plugs [hence explaining the hill issue], so he replaced those. But this did nothing to help with the noise.
2015 Suzuki Celerio, automatic transmission, with 30,000 miles on it. It has been serviced religiously every 6 months / 2,000 miles. 3-cylinder engine.