The other day I dropped my car off at a European specialist shop, and while I was there, a technician was working in the engine bay of a Mk7 Golf R, cleaning out carbon deposits off the intake valves.

Back in the 1980s, it was common for your average family sedans to produce less than 150 horsepower from internal combustion engines that weren’t all that small. I still can’t believe we drove ...

Modern engines are cleaner and more efficient than the ones you grew up with, yet many drivers are discovering a new headache: stubborn carbon crust building up on intake valves. Understanding why ...