2008 Audi S5 Repair and Maintenance
A guide to problems, costs, maintenance and repair for your 2008 Audi S5
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2008 Audi S5 ProblemsDecreased Power and Fuel Economy from Carbon Buildup
The 2008-2017 Audi S5 3.0TFSI and 4.2FSI is subject to carbon buildup inside the engine causing power loss, check engine light, and a rough idle. In normal vehicles, the engine is cleaned by the gasoline flowing through, however, these cars use direct injection so gasoline is rerouted away from common carbon buildup areas.
The solution is to remove the intake manifold and professionally clean the intake manifold, intake ports on the cylinder head, and the intake valves. This may need to be done in as few as 20,000 miles.