GEES97TA

The other day i went to the carwash which i never do but i was running late to go to a car show so i had no choice,anyway it is a hand wash and it was crowded as hell and this was Saturday it was hot out so i had the air on while sitting in the line the temp wasnt crazy hot or anything but when they were done i left the lot and the car was Pinging real BAD and it blew a little puff of black smoke out as soon as the car cooled down maybe 5 to 10 minutes it never did it agian i drove it tonite and its fine. What could have happend and what was it?????