Carbon Buildup Issues in GDI Engines

A 2021 Mercedes-Benz GLC300 owner experienced misfires on cylinders 2 and 3 at 89,000 miles. The initial diagnosis pointed to a faulty injector, but after replacement, the issue persisted. Further investigation revealed heavy carbon buildup on the injectors. GDI engines are prone to carbon buildup on intake valves, which can cause rough idling, misfires, and performance loss.

This is because fuel never washes over the intake valves in these engines. According to automotive engineering sources, periodic intake valve cleaning can prevent these issues. Carbon buildup can be addressed through methods such as walnut blasting or chemical treatment. The problem is not unique to Mercedes-Benz, as other manufacturers like BMW and Audi also use GDI engines that can be susceptible to carbon buildup.

Owners of high-mileage GDI vehicles may need to consider proactive maintenance to prevent these issues.