- Engine / equipment
- 4.2 V8 40-valve (S4 B6/B7) and 4.2 FSI V8 (RS4 B7, S5 8T until 2011, RS5, R8, Q7 4L)
- Period mentioned
- 2003–2015
- Symptoms
- Rattle from the rear of the engine on a cold start, misfires or an engine light for timing deviation; on FSI engines, power loss and rough idle from carbon build-up.
- Possible cause described
- The timing chains sit at the rear of the engine, against the bulkhead, with plastic guides and tensioners that crack; replacing them means removing the engine. FSI direct injection builds carbon on the intake valves from about 40,000–60,000 km.
- Check for the garage
- Listen to a cold start, read crank-cam correlation codes and inspect the intake valves with a borescope.
- Cost cited in the source
- Chains (engine out): approx. €6,500–11,000 on a Q7 4.2 FSI (converted from dollars); carbon cleaning: far lessA rough figure from the original database, not an up-to-date quote.
Mileage cited in the database: from 40,000 km. This is not a maintenance interval and does not predict a failure.