Ask the Expert: What causes carbon deposits in GDI-equipped vehicles?

Jan. 27, 2016
The cause of carbon buildup can vary by vehicle make.

Q: What causes carbon deposits in GDI-equipped vehicles?

A: The cause of carbon buildup can vary by vehicle make, as engine management systems can mitigate the carbon buildup in certain vehicles by something as simple as an ECU update. Essentially, carbon buildup occurs due to a combination of low quality fuel, short, frequent cold weather trips or positive crank case ventilation which may leave an oily layer around the intake valve. These factors, in conjunction with the operating temperatures of the engine casing, lead to a buildup of carbon deposits.

Timing may also have an effect if the intake valve stays open long enough to be exposed to unburned fuel. Finally, the location of the GDI injectors in the cylinder head plays a significant role in carbon buildup because it does not allow for the fuel sprays to reach the back of the intake valve, making it difficult to keep the intake runners and valve clean. 

Information provided by: Robert Bosch LLC

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