BLS - AGR errors and jerking during acceleration when in limp mode

Hello again.

Caddy 3 with BLS engine.
Wiring harness for engine, approximately 225,000 km.
Long-distance vehicle (rarely just "short-distance vehicle").
Bj Motor: 2007 (Engine year: 2007)

Already checked.
- The AGR (Abgasrückführung - Exhaust Gas Recirculation) system was removed and a control element test was performed. It was removed because the measured values during the AGR system test were not correct. AGR was not carbon fouled!
- Connectors for air mass meters and other sensors.


"When driving with a warm engine at a constant speed with very little throttle, the EGR error 'P0402 - 000 - Throughput too high - Warning light ON' occasionally appears."
When I restart the engine, I also get the error code from the mass airflow sensor: "P0101 - 000 - implausible signal."

If the engine experiences a misfire, will there be a jerk or hesitation during acceleration, similar to what you might feel if the variable turbine geometry (VTG) of the turbocharger were stuck? "It works perfectly fine when the car is stationary (although that doesn't necessarily mean anything). Once the initial combustion phase is over, the car runs smoothly again without that jerking."

I've attached a log file that hopefully contains all the necessary data. The problem with the log was that it happened during the initial burn-in phase.
However, the combustion process doesn't seem to be working correctly either. The temperature inside the particulate filter never exceeds 500°C; it's usually between 400 and 450°C, and only slightly above 500°C under heavy load.

Just a note about the log: From second 28 onwards, I only gradually pressed the accelerator pedal, because that's when the jolt is most noticeable.
What I find particularly noticeable are the target and actual values of the EGR (Exhaust Gas Recirculation) system.

Where could the problem be? - Possibly the mass airflow sensor? Cable broken?

Thank you again for your help (hopefully).

Hello,

Code:

Block Abgasrückführung - (Istwert)   MARKE   Ansteuerung - Abgasrückführung mg/H       % 5   0,17   100,6 5   1,05   100,6

Your air mass value is much too low. The engine control unit (ECU) is also indicating that the mass airflow sensor might be faulty.

In terms of quantity, the expected air mass in idle mode with active EGR is approximately 230-280 mg/hour, while without EGR it is around 480 mg/hour.

But not 5mg/H.

Besides a new lambda sensor, which is likely giving you a false reading at 480,000 km, you should also check if the intake manifold is mechanically sound.
So, to make sure the intake manifold hasn't detached from the turbocharger inlet, that the intercooler pipes are properly connected, etc.

Also, please check the wiring to the mass airflow sensor as well.

Best regards, Rainer.

Hello and thank you for the quick response!

The issue seems to be resolved again. -> Air mass sensor!

I checked all the hoses, etc., but everything was dry, tight, and visibly leak-free!
Then I remembered that I still had a VEMO mass airflow sensor (original equipment quality). I had removed it at the beginning of the year because I thought it didn't seem 100% okay, as it was showing symptoms similar to those described in my old thread:

/viewtopic.php?t=31040&highlight=unround+air+conditioning

At that time, when the linked thread was created, and every time the air conditioning was on, the engine ran roughly at idle. After replacing the mass airflow sensor, the problem suddenly disappeared. This mass airflow sensor was a "Meat & Doria quality equivalent." This mass airflow sensor was working properly until just a few minutes ago. The existing VEMO mass airflow sensor exhibited the same symptoms as described in the thread above, namely, an unstable idle when the air conditioning is turned on.
Okay, I reinstalled the VEMO unit to test it, and suddenly the engine is running as it should. Even with the air conditioning on...

At the beginning of the year, the engine started emitting a stronger smell in the exhaust, and I thought it might be a problem with the injectors. Since then, I've only been using premium diesel without any biofuel additives. Now the engine smelled better again, regeneration occurred less frequently, and fuel consumption was also reduced by 0.3 liters per 100 kilometers.

Just a few days ago, I had to refuel with regular diesel again, and since then, there has been this jerking sensation during the diesel particulate filter regeneration process. HOWEVER, the engine no longer smells like it did at the beginning of the year, before I started using premium diesel!

Since the VEMO mass airflow sensor now seems to be working properly (although we still need to wait and see how it performs in different outside temperatures...), could it be related to the fact that I've been using "Premium Diesel" fuel for about six months? You can also find online that this type of fuel is supposed to have a cleaning effect. Possibly, the injectors were or are slightly clogged or carbonized.

Hello,

Premium gasoline is certainly not bad, but its effects are limited. It's likely that the nozzle holes of the injectors are less prone to carbon buildup. Problems related to long periods of inactivity (months or more), such as clogging or sludge formation due to decomposition processes and microorganisms in the fuel, can also be avoided with this solution.


Then we've probably reached the end of the road.

LLMs (Large Language Models) rarely fail completely. However, many older models were of poor quality. And if so, then due to contamination or adhesion caused by oil, for example, from sports air filters, or excessive emissions from the catalytic converter.

Best regards, Rainer.