With no fuel flowing through the inlet, this direct injection V8 clogs up with carbon deposits
and other direct injection motors with its decoking process.‘ In 2012, the B8 came in; they don’ t seem to suffer as much.’
The later RS4’ s engine, the CFSA, still has direct injection so carbon still builds up. So while some details may differ from other cars, the information within this feature will apply to other direct injection engines.
What causes the fault?
Direct injection – where a fuel injector sprays fuel into a combustion chamber rather than an inlet port – has many clear benefits. The exact and targeted nature of direct fuel injection makes for more efficient, better-performing engines that produce fewer emissions.
There’ s a major downside to direct injection, though. These engines don’ t benefit from the cleaning effect that fuel has as it flows through the intake and over the intake
valves.‘ This means that the surfaces in the intake are prone to any oil or contamination in the airflow to“ stick” to it,’ says Steven.
The B7 RS4 is one of Audi’ s hits, it looks, drives and sounds spectacular
Spring 2026 The Engine Rebuilder 53