Audi A8 Quattro Problems

Various bushings—located around the subframe, suspension, and steering—deteriorate with age. A clunking noise when driving over bumps, accelerating, or stopping may be a sign of worn bushings.

Popping sounds from the rear of the vehicle may be heard moments after starting the engine, or when slowing to a stop. This noise is from the leak detection pump filling the fuel tank with air, and releasing to retest the system when it finds a fault. The sequence of faults identifying this issue are as follows:

• Succession of loud pops from rear of vehicle
• Pops go away, and fuel economy decreases 
• Check engine light illuminates
• OBD trouble code P2404 and/or P0441 is stored
• Engine will not start after refueling (must crank for over 30 seconds)
• Vibration when slowing to a stop

The cause is a valve which is mounted on the front of the intake manifold, commonly called the N80 valve, or EVAP system purge valve. The valve is designed to open under specific circumstances, but a worn valve will remain open at all times, preventing the pressurization of the fuel tank. 

Correction of the issue is to replace the N80 valve with the latest revision. 

The 2007-2017 Audi A8 with FSI/TFSI, including the W12 are direct injection engines. These engines are subject to carbon buildup in the intake system which can cause power loss, OBD codes and a check engine light, and a rough idle. In normal engines, the engine is cleaned by the gasoline flowing through the injectors and into the intake system, however, the A8 uses direct injection so gasoline does not flow through common carbon buildup areas. 

Possible trouble codes include: P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0309, P0310, P0311, P0312.

The solution is to remove the intake manifold and professionally clean the intake manifold, intake ports on the cylinder head, and the intake valves. This may need to be done in as few as 20,000 miles. 

Clogged drains can allow rainwater to accumulate in the plenum tray (at the base of the windshield). The water may leak into the vehicle's interior, brake booster, or electrical components, which can lead to major problems. Our technicians recommend keeping the tray clear of leaves, pine needles, and other debris.

The thermostat may erratically stick open or closed. The can result in illumination of the Check Engine Light and/or engine overheating.

A problem with the torque converter can cause the Check Engine Light to illuminate.

Premature wear in various multi-link suspension components can cause noises that are difficult to diagnose. Worn suspension parts can also cause uneven tire wear and create steering alignment problems.

A fluid leak may develop from the propeller shaft seal on the rear of the transmission. Our technicians tell us that replacing the seal will commonly correct this concern.

Our technicians recommend having the constant velocity (CV) boots and CV joints inspected at each service. Servicing torn CV boots early can prevent the need to replace the CV half shaft or CV joint.