Audi AMB Service Manual page 231

ENGINE 1.8 Liter 4-Cyl. 5V Turbo Engine Mechanical, Engine Code(s): AMB
With VAS5051 diagnostic tool connected:
Erase DTC memory.

Effects of leakage at exhaust end
Effect: Charge air pressure too low, possible exhaust smell, soot traces in engine compartment

Possible fault sources:
1 - Connection between turbocharger/exhaust manifold
2 - Connection between exhaust manifold/cylinder head
Mechanical air recirculation valve, checking
NOTE:
The mechanical air recirculation valve is located upstream of

turbocharger. It is opened by vacuum via the Recirculating valve for
turbocharger N249 when the engine is on overrun, idling and partial load.
This reduces charge air pressure upstream of throttle valve, thereby
keeping turbocharger rotating at higher speed.
Check the mechanical air recirculation valve if the engine is not producing

full power or if it jerks when the throttle is opened and closed.
Special tools, testers and auxiliary items required
Fig. 303: Identifying Hand Vacuum Pump V.A.G. 1390
Courtesy of VOLKSWAGEN UNITED STATES, INC.
2005 Audi A4 Quattro
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