Popping in exhaust
Coca cola works better, it has sugar in it. But really, a pint of water like that being cold, makes the hot carbon pop off the metal. I have seen it done so many times, and work. And never hurt a thing, but the crap shooting out the exhaust...
Before I went to work for a dealership, I worked for a friend's dad, who owned a service station right in the middle of town, where all the old widows lived. Cars running bad- sent my young butt out on the expressway to blow out the carbon. That didn't get that 2 years of putt-putting for 10 blocks to the store and back? Coca cola. Lol.