AGR Behavior in ALH 66kW Engines

Hi everyone,

I drive a Golf 4 ALH with 66 kW. I have a question about the AGR system. Unfortunately, I couldn't find anything relevant using the search function, and Ulf's post didn't really answer my question.

Does the engine only operate with exhaust gas recirculation (EGR) during partial load conditions? Or also during idling? I once read somewhere that the diaphragm actuator, which controls the EGR valve, fully actuates the EGR valve immediately after the engine is started and then gradually retracts it as the engine power increases.
Bei meinem ALH tut sich im Leerlauf garnix. Wenn man die AGR-Klappe von Hand verstellt (sie ist leichtgängig und hakt nicht), geht der Motor einfach aus, wenn man die Klappe in den Anschlag bringt. Is that possible?
I have the feeling that something might not be quite right with the EGR system. I've noticed several times that the car accelerates moderately up to about 3000 RPM, and then suddenly experiences a significant surge of power. This is particularly noticeable in second and third gear.
The car has actually had this problem since the beginning (manufactured in February 2001, 30,000 km).
Nothing can be found in the error memory.

Does anyone have an idea how to check the function of the AGR (Abgasrückführung) without simply disabling it?

Regards,

Eike.

Hello,

The AGR (Abgasrückführung) system doesn't have a valve; it has a flap. The valve you're referring to is the throttle valve, which is used to dampen the "engine knock" of diesel engines when they are turned off.

The AGR (Abgasrückführung system) is active for a certain period, even when the engine is idling, but then it is deactivated. It is also inactive at full load.

Have you checked the VTG adjustment and the associated valve?
Has a measurement run already been carried out?

Hi Michael,
I was told at the workshop that the throttle valve adjusts the air-fuel mixture by controlling the ratio of exhaust gas to fresh air, depending on its position. The exhaust gas recirculation pipe also runs from the exhaust manifold to this valve.
'Where exactly is the AGR valve located? I'm not referring to the electric valve that controls the membrane dosage, but the mechanical one that prevents exhaust gas recirculation at full throttle.'

I once conducted a measurement run using a makeshift LDA (Laser Doppler Anemometry) system and observed that the boost pressure only reached its maximum (!!) in 5th gear, at over 3000 RPM. In all other gears, the boost pressure was already at its maximum around 1900 RPM.

I'm currently in the process of installing a fixed LDA (Laser Doppler Anemometer) to verify the measurements.
Let's see what happens.

Regards,

Eike.

Unfortunately, the workshop has given you some incorrect information. The EGR valve is located in the same metal pipe as the shut-off valve. If you look at the pipe from the front, and the shut-off valve is on the left, the EGR valve is located a bit further to the right and downwards. A metal flexible pipe runs from the EGR valve to the exhaust pipe.

Michael II wrote:

Unfortunately, the workshop has given you incorrect information. The EGR valve is located in the same metal pipe as the shut-off valve. If you look at the pipe from the front and the valve is on the left, the EGR valve is located slightly further to the right and downwards. A metal flexible pipe runs from the EGR valve to the exhaust pipe.

... no offense, Michael, just to avoid any further misunderstandings:

The EGR valve is actuated by a thick diaphragm housing that is attached to the intake manifold. A rod extends from the diaphragm housing through the intake manifold, which opens and pushes the lower hole towards the exhaust pipe.

If you remove the hose angle located before the shut-off valve, you can see the EGR valve inside the pipe behind the valve.

Hi everyone,

'Today, I installed an LDA (Lambda-Sonde) and noticed some unusual behavior in the boost pressure: When accelerating from 1500 RPM with the throttle fully open, the boost pressure increases from approximately 1800 RPM to 1.2-1.3 bar. This pressure remains stable for about 2 seconds and then quickly drops to 0.5-0.6 bar. From this point on, the pressure only increases very slowly as the engine speed increases.'
Actually, it should be regulated to about 0.9 bar right away, shouldn't it? I also have the feeling that the boost cut-off starts a bit late. In my old Golf 3, the pressure spikes were much shorter, and the boost pressure was consistently at 0.95 bar afterwards.
Sollte da vielleicht etwas mit der VTG-Verstellung nicht ganz hinhauen oder schwergängig sein? What do you mean?
This behavior regarding boost pressure also explains why the car feels a bit sluggish. If there isn't proper boost pressure, the mass airflow sensor (MAF) reports lower values, and the fuel injection amount doesn't reach its maximum.
What's the best way to explain this to the workshop? The car is only 6 months old. Will they install a new turbocharger right away?

Regards,

Eike.

Hello Eike,

From my gut feeling, I would say something is stuck in your VTG (Variable Turbine Geometry). If your vacuum actuator is also installed "upside down," meaning the vacuum hose comes out from the bottom, check if there's any dirt or debris blocking the opening at the top where the adjustment rod goes into the actuator.
In this case, use compressed air to blow into the gap between the adjusting rod and the can, while simultaneously moving the lever.
If you are not comfortable with the "risk" of having the turbocharger replaced by the workshop, you can loosen the two 10mm nuts that secure the vacuum actuator to the turbocharger. This will allow you to check the free movement of the VTG (Variable Turbine Geometry) mechanism inside the turbocharger without disconnecting the adjustment rod.

Best regards, Rainer.

@eike

Check this out:

www.ralfhandel.de/ladedruck.jpg

www.ralfhandel.de/ladedruck2.jpg (axis labeling as in the first image, time axis in seconds)

I recorded it on Tuesday. It's a Skoda Octavia Combi 1.9 TDI with 66 kW (VTG turbocharger, engine code: ALH). It has an automatic transmission.

CU Gremlin.

Hi Gremlin,

suspicious... at least with my AHF (presumably referring to a specific type of equipment or process), the settings are adjusted much faster, without the long initial "undershoot."
You can find pictures of the intake processes in my engine, for example, in the VTG article.

Best regards, Rainer.

'However, this isn't noticeable in the acceleration. I also can't suddenly apply full throttle (as you can see from the setpoint curve), otherwise the torque converter clutch will immediately engage.'

It prints smoothly without any waves, jerks, or other imperfections.

only when operating at a constant speed of around 70 km/h does it vibrate slightly, but at that speed, the engine is running at 1500 RPM. This is just about the minimum operating speed of the turbocharger, and the cruise control system then tries to compensate for the speed and oscillates. When using the accelerator pedal, everything is fine.

See you, Ralf.