Exhaust gas recirculation at idle speed for engine: AXR

"On my VW Golf 4 Variant 1.9 liter with AXR engine, with a mileage of 170,000 km, manufactured in 2005, the air mass flow target value in channel 3 (exhaust gas recirculation) is 195 mg/H at idle speed. The actual value is approximately 220 mg/H. The EGR rate is 74.5%. After about 2.5 to 3 minutes at idle with a warm engine, the actual value suddenly changes to approximately 460 mg/H and the EGR rate drops to 4.8%. A slight hesitation of the engine can now be felt at idle." After a very brief surge, the value then returns to approximately 220 mg/H.
I replaced the AGR valve (from Pierburg) and performed a basic adjustment. I also replaced the mass airflow sensor (from BOSCH). I cleaned the throttle valve. There are no error codes stored in the engine control unit's memory, and there were none before the repair either. The engine is consuming a small amount of coolant, approximately 100ml every 4 weeks. I checked the cooling circuit for leaks, and the pressure gauge didn't drop after about 30 minutes.
The target and actual values of the turbocharger are within the acceptable range. I checked the intake path from the air filter, through the turbocharger, and onward for leaks, and everything seems tight. However, there was significant leakage detected at the bottom, near the engine block, specifically around the dipstick tube. The crankcase ventilation system is working correctly, as measured with the Hazet test device (hose gauge).
Can anyone give me a tip or explain why the engine slightly sputters when idling for about 2.5 to 3 minutes?
Best regards,
Klaus.

Hello,

The behavior seems normal, except for the slightly too low setpoint value.

Quote:

Can anyone give me a tip or explain to me why the engine slightly jerks when idling after about 2.5 to 3 minutes?

Check the fuel injection amount; if the engine control unit detects it as too low, it can cause the engine to jerk or misfire. In this case, check the values of the idle speed control and the settings of the PD elements.
Check if activating high-power electrical consumers eliminates the jerking (e.g., rear window defroster, seat heaters, etc.).

Best regards, Rainer.