KNOWN FAULTS · Audi

Audi A4 (B6) S4 (4.2 V8) common problems.

2000–2004 · 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 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.

Applies if: All versions; AUTO BILD cites the cluster fault for the 2000–2004 A4.

Will not start because of the immobiliser on the Audi A4 (B6) and A6 (C5)Electrical and electronic systems

Engine / equipment: Audi A4 2000–2004 (B6) and A6 1997–2004 (C5), all versions
Period mentioned: 1997–2004
Symptoms: The car will not start because the immobiliser blocks it. On the A6 the central locking, windows and battery also often fail.
Possible cause described: AUTO BILD says that on the 2000–2004 A4 a faulty immobiliser often prevents starting, and that the repair is a new instrument cluster (which houses the immobiliser), for about €500. On the 1997–2004 A6 it lists the immobiliser, central locking and window regulators among the main culprits for electrical faults, plus a battery that often fails.
Check for the garage: First test the battery: with low voltage the immobiliser fails too. Try the spare key. If it still will not start with either key, the garage diagnoses the immobiliser in the cluster with Audi equipment before replacing the cluster, because the keys have to be matched.
Cost cited in the source: About €500 for the instrument cluster (AUTO BILD, 2008).A rough figure from the original database, not an up-to-date quote.