AGR Function: Basic Settings Mode

Hello diesel mechanic, I noticed something on our company car (this is my second attempt at checking).
that the air mass readings do not match the target values when the EGR system is both inactive and active.

I performed the check using VAGCOM, specifically in the basic settings mode (measuring block 03).

With the EGR system deactivated, for the 1.9L engine, the air mass should be between 450 - 500 mg/stroke (the measured value was approximately 550 mg/stroke).
and when the EGR system was active, it was approximately 150 mg/stroke (target value is about 250 mg/stroke, which is half of the value when the EGR system is inactive). Source: (technical article, target value table, VAGCOM specifications).


During this diagnosis, the engine temperature was approximately 90° and there were no other problems.
However, this afternoon during my first attempt (engine temperature < 80°), I noticed relatively strong vibrations in the engine and an uneven running sound (during the start of the test and as the RPM increased).
"After that, I also stopped the test. The vibrations normally occur between 1000 and 1400 RPM (which is what led me to the diagnosis), but they have never been as strong as during the test. What could be causing the vibrations and the altered running behavior? A connection with the EGR system and possibly the turbocharger pressure control (since it's linked to the EGR system) cannot be ruled out."


According to the technical article, highly scattered values for active or inactive AGR (Ausgleichsregelgerät - exhaust gas recirculation) indicate a stuck membrane valve, which I will also replace.
It could also be the control valve that's causing the issue, but it's not a connection problem since the connection is secure and tight.

The technical article does not mention any changes in motor vibration or altered operating characteristics.

More results regarding air mass and intake manifold pressure.

[Air mass, measurement block 010 - 3rd gear 3000 rpm] Target value: 850 - 1050 mg/H. Actual value: approximately 907.9 mg/H.

[Boost pressure, measurement block 011 - 3rd gear 2850 - 3150 rpm] Target value: 2000 - 2150 mbar. Actual value: approximately 2152.2 mbar .

So far, everything is fine.

Nal_rA wrote:

When the EGR system is inactive, the air mass value for the 1.9 l engine should be between 450 - 500 mg/stroke (the measured value was approximately 550 mg/stroke). and when the EGR system was active, it was approximately 150 mg/stroke (target value is about 250 mg/stroke, which is half of the value when the EGR system is inactive). Source: (technical article, target value table, VAGCOM specifications).

Hi,

As far as I know, the target values apply to driving or idling conditions, but not to the initial settings.
If a whopping 550 mg/stroke is entering the cylinders at 1400 rpm with EGR off, that's likely due to the boost pressure being supplied by the turbocharger.
Under normal idling conditions, all values are likely to be within the specified limits.

The engine shaking during startup to the test speed is caused by a software issue. For example, mine does this when I change the low-speed setting through adaptation while the engine is running.

P.S.: It wouldn't be a mistake to post which car and engine code you were working on.

ulf wrote:

Under normal idling conditions, all values are likely to be within the specified limits.

Okay, in normal idle conditions (i.e., at 830-900 rpm), the actual values are within the target range of 230-420 mg per stroke.

Today, I had the opportunity to replace the pressure sensor on our 1.9L engine (engine code: AJM), which is connected to the membrane valve that controls the throttle valve.
When there is a vacuum, it closes; otherwise, it is always open. If the flap does not close properly, this is often related to vibrations and jolting issues.
-> when turning off the engine. Now, when I turn it off, there are no more noises or jerks; it's very pleasant .

The EGR valve is also slightly clogged. I will soon be replacing or cleaning the intake manifold, the EGR valve, and the EGR control valve.
I still need to think about whether I should completely deactivate the AGR (Exhaust Gas Recirculation) system. Given the high air mass that the MAF sensor is measuring, a significant amount of exhaust gases are being allowed through, and eventually, the problem will likely reoccur.

The small pressure sensor (top) and the EGR control valve N18 (right), together with the EGR valve.
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And? What did the change bring you?