Document: Quacking sounds from AGR, AJM, and ATJ engines. (Solution)

AJM-/ATJ-Engine
Exhaust backpressure (pulsation noise) of the EGR system at idle.

Cause: When the engine is idling and warm, a constant vacuum is connected to the AGR valve. In some cases, the vacuum may not be constant, but pulsating, at the AGR valve. In the same rhythm of the fluctuating negative pressure, the membrane of the AGR valve begins to vibrate, connected
with loud croaking sounds. This doesn't happen all the time, but only sporadically when the air column in the vacuum line between the solenoid valve and the EGR valve is "energized".

Procedure:
If the "quacking" sounds cannot be determined during a test drive, the air column in the vacuum line between the electromagnetic valve and the EGR valve can be stimulated by rapidly opening and closing the throttle valve below the EGR valve. If the throttle valve is closed too far, the engine will stall. Once stimulated, the vibrations remain, and consequently, the membrane's quacking sound persists.
Not to remove the AGR valve, it cannot be responsible.
Instead of the three-part vacuum line between the AGR valve and the solenoid valve, use a solid woven line.
hose size N 020 282.1 (Meterware) to be laid and connected with cable-
bind and fix. The length should be chosen so that it cannot be folded or torn.