Mercedes W204 C200 CDI: Engine Misfire at Idle

I have a C200CDI with a 646.811 engine (2.2L, 100kW) that starts making a sawing noise about 20 seconds after starting in idle. It lasts for approximately 100 revolutions. I initially thought it might be related to the EGR valve. At first, the air mass reading is around 370mg/h, but if I let it run longer at idle, the air mass increases to 550mg/h and it shuts off, but the sawing noise persists.

Has anyone else experienced this?
There were two errors in the error memory: 22FE, which indicates a problem with the throttle valve, and another error related to the turbocharger pressure control. I don't remember the exact code for the second one, but I can provide it tomorrow.

Hello,

Quote:

22FE Throttle valve

It could already be the cause: what if the airflow to the engine is temporarily severely restricted because the valve is malfunctioning?
Could you temporarily "hold" the flap in place for testing purposes, or generally check it?

Best regards, Rainer.

Thank you, Rainer.
I'll take a closer look at it tomorrow; first, I need to find out where the throttle valve is located.
However, it should then also cause problems during normal operation...

You can't adapt the video about that specific car to your own vehicle because it has a completely different engine (OM651).

"I also experience these slight fluctuations in my E-Class with 646,821 kilometers, and they've been present for a long time without any negative effects. However, I don't notice anything unusual about the engine performance; it's just that the needle fluctuates slightly."

You can also tell by how the engine runs.

I checked the throttle valve, but I couldn't find any faults.
However, the vacuum sensor for the intake manifold control is defective. I adjusted it to every position while the engine was running, but it didn't change anything about the fluctuations.

After an extensive test drive, I was able to let it idle for 3-4 minutes without any fluctuations. I turned off the engine and restarted it, and after 20 seconds, the fluctuations reappeared.

Have you ever plotted the rail pressure (actual vs. target) against the engine speed? Perhaps a correlation can be found there.

Problems with the fuel pressure regulation can cause this (essentially, fluctuations around the target pressure). Beyond a certain point (X), the fluctuation becomes so dynamic that the engine control unit can no longer compensate for it, which then affects the amount of fuel injected and thus the torque produced. This is a common issue in Ford vehicles.

I checked the rail pressure, and it's fluctuating, but those fluctuations are caused by the engine running roughly. I don't remember offhand what the target value should be.
Next time, I need to check if I can also view the target and actual values using VCDS via EOBD, as that would allow me to record them. My multi-brand diagnostic tool doesn't offer this functionality.

I believe that's not possible through EOBD. It only shows the actual pressure value.