Audi A4 (B6) common problems.

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.

Sources from the original database

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.

Sources from the original database

Engine / equipment

1.2, 1.4, 1.9 and 2.0 TDI unit-injector (PD) engines, including the VW-sourced 2.0 CRD in Chrysler, Dodge and Jeep

Period mentioned

2000–2010

Symptoms

Growing noise from the cylinder head, power loss and rough running (cams and lifters); unstable idle, smoke or hesitation (injectors); on the 16-valve 2.0 TDI, coolant loss with no visible leak from a cracked head.

Possible cause described

The camshaft also drives the unit injectors and carries a heavy load: without VW 505.01 oil the lobes and lifters wear. 2.0 TDI PD injectors fail frequently. Some 16-valve 2.0 TDI heads (part number ending in A) crack; VW considered it fixed by the end of 2006.

Check for the garage

Check the oil history (VW 505.01), listen to the head, check injector balance rates with a diagnostic tool and, on the 16-valve 2.0 TDI, read the head part number (03G 103 351) and look for coolant loss.

Cost cited in the source

Camshaft and lifters: approx. €400–800; 2.0 TDI PD injectors: €900–2,000A rough figure from the original database, not an up-to-date quote.

Mileage cited in the database: 120,000–200,000 km. This is not a maintenance interval and does not predict a failure.

Sources from the original database

Engine / equipment

2.5 TDI V6 with distributor pump: Audi A4 (B5 and B6), A6 (C5) and VW Passat B5

Period mentioned

1997–2005

Symptoms

An engine that runs rough, loss of power or hesitation; now and then the injection pump fails; oil leaks from the engine or gearbox.

Possible cause described

AUTO BILD (March 2008) reports more and more complaints about the A4's 2.5 V6 because of worn camshafts (Audi did not issue a recall) and adds that the Multitronic gearbox fails mainly with this engine, because of its high torque. On the A6 (1997–2004), AUTO BILD lists faulty air mass meters causing loss of power or hesitation, injection pumps that fail now and then and oil leaks from the engine and gearbox, mainly on the TDI. The Passat B5 has the same engine.

Check for the garage

If the engine gets noisier or runs worse with the miles, have the garage check the camshafts by removing the cam covers. Read the codes and test the air mass meter before touching the pump. With the Multitronic gearbox, ask for its history and check that it does not jerk or slip.

Cost cited in the source

No verified estimate; ask the garage for a quote.A rough figure from the original database, not an up-to-date quote.

Sources from the original database

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.

Sources from the original database