Common issuesOne of the 5.3-liter Ecotec 3 engine's high-tech features, while it can contribute to fuel savings, has also led to some of the engine's common problems. Direct injection is a technology where the fuel is introduced into the combustion chamber of the engine's cylinders directly and not via the cylinder head's intake valves. While this allows for precise fuel metering, the flow of fuel through the valve system helps keep the valvetrain clear of carbon buildup.Without this cleaning action, deposits of oil and unburned fuel can build up in the intake ports and cylinders, causing loss of power and fuel economy and rough idling. The best way to clean these deposits is to remove the intake manifold and clean the ports with crushed walnut shells, a process known as walnut blasting.Direct injection also requires a fuel pump that operates at very high pressures, sometimes up to 1,500 psi. (By contrast, a 2000 5.3-liter LS series engine requires about 50–60 psi of fuel pressure.) This high demand can lead to pump failure. Direct injectors are also subjected to very high heat inside the cylinders and can often fail and stop delivering fuel, leading to a cylinder misfire.