KNOWN FAULTS · Audi

Audi A4 (B7) S4 (4.2 V8) common problems.

2004–2008 · Petrol

Sources are not verified in real time and no entry confirms that your car is affected.

3 known faults with sources

4.2 V8 rear chains and carbon build-upTiming / intake

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.

Applies if: Only if fitted with the air conditioning system described.

A/C not cooling: N280 valveClimate control

Engine / equipment: Air conditioning with clutchless compressor and N280 regulating valve (combustion VW, Audi, Seat, Cupra and Skoda from 2006)
Period mentioned: 2006–2026
Symptoms: The air does not cool or cools intermittently (for example only at motorway speed), and sometimes the compressor rattles with the A/C on. Codes 01232 (N280 valve), P2612 or 00898.
Possible cause described: The compressor regulates its output with the N280 solenoid valve, its most common failure point. Audi issued technical bulletins over a manufacturing fault in this valve on Sanden compressors. Its connector can also become brittle and corrode (especially without the engine undertray), or the wiring fails.
Check for the garage: Read the codes and N280 control current with VCDS or ODIS, measure its resistance (about 10 ohms) and check the connector and wiring before replacing parts. If the valve or compressor is replaced, the whole circuit must be flushed.
Cost cited in the source: N280 valve: a cheap part (about 30 dollars) where sold separately; new compressor with circuit flush: considerably moreA rough figure from the original database, not an up-to-date quote.

Applies if: Only if fitted with the automatic gearbox described in the record.

Audi Multitronic (CVT) gearboxAutomatic gearbox

Engine / equipment: Multitronic continuously variable gearbox (01J and successors) in front-wheel-drive Audis: A4 B6/B7/B8, A5 8T and A6 C5/C6/C7
Period mentioned: 2000–2014
Symptoms: Judder or vibration when pulling away (especially uphill), a slipping feeling at low revs, jerky acceleration and limp mode with limited speed; sometimes a burning smell.
Possible cause described: Known failures of the variator chain and pulleys, the hydraulic and electronic control unit and the clutch pack. Audi issued service bulletins, and forums report failures even with the recommended fluid changes, although poor maintenance speeds them up.
Check for the garage: Read the gearbox codes with Audi-compatible equipment, check the fluid change history and, at a specialist, judge whether fluid and a clutch adaptation are enough or the control unit or variator needs repair. With limp mode or a burning smell, stop driving.
Cost cited in the source: A UK specialist says a judder checked early usually costs a few hundred pounds, while ignoring it can end in a full rebuild.A rough figure from the original database, not an up-to-date quote.