How to clean intake deposits in direct-injection engines | Articles

When direct injection came onto the scene 10 to 15 years ago, it seemed to cure many of the world’s problems, offering more power and improved fuel economy. Where traditional injection setups squirt the fuel into the intake port, direct injection delivers a very precise amount of fuel right into the combustion chamber.

But a problem tended to crop up: carbon buildup in the intake manifold and on the backs of the valves, especially the intake valves. Too much buildup, as you can imagine, isn’t good for engine health or efficiency. Regular maintenance for many owners of direct-injected engines included walnut shell blasting, including the laborious disassembly of the top end of the engine. 

Two factors, notes Zachary J. Santner, senior specialist of quality at Sunoco, contribute to that buildup: oil that has seeped past the valve seals and the oily crankcase blowby vapors that are rerouted back into the combustion chamber. When those hydrocarbons are super-heated yet not burned, they form solids via the coking process.

In a traditional, port-injected engine, Santner continues, the incoming fuel cleans away those oil deposits. A direct-injected engine, of course, lacks that feature. 

So, what to do? Use of a Top Tier fuel, like all the pump products from Sunoco, he continues, will still help clean several major parts of the engine–specifically the injectors, combustion chamber and piston tops.

In addition to walnut shell blasting of the intake and valves, Santner notes some other measures that can help. While he has no direct experience, he does note that motor oils specifically designed for direct-injected engines are coming onto the market. These products claim to be more resistant to the coking process.

Solvent cleaners also exist, and Santner notes that the safety data sheet for the GDI IVD Intake Valve & Turbo Cleaner from CRC Industries lists a rather large dose of detergent. The product also contains a carrier suitable for delivering that solvent to the right places, the intake manifold and backs of the valves. 

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