OM647.961 (W211 E270 CDI) – Loud Engine, Cylinder Correction Issues, Intermittent Idl

Oct 3, 2025 | 01:02 PM

YourGothDaddy

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Mercedes-Benz W211 E 270 CDI OM647.961

OM647.961 (W211 E270 CDI) – Loud Engine, Cylinder Correction Issues, Intermittent Idl

Hello everyone,

I own a 2003 Mercedes W211 E270 CDI with the OM647.961 engine (CR3 system, 177hp). I need some advice because I’m running into issues that I can’t fully diagnose, and I’d like to approach this carefully since I’m on a tight budget.
Symptoms

Engine has good power and accelerates fine.
However, it is noticeably loud.
At idle, it sometimes shakes intermittently.
There is a constant clicking/ticking noise, especially noticeable at low revs ( or at least then I can hear it ) (below ~3000 RPM).

Diagnostic Values (injector corrections)
Cylinder 1: +0.58 mm³/stroke
Cylinder 2: –0.84 mm³/stroke
Cylinder 3: –2.70 mm³/stroke
Cylinder 4: +5.10 mm³/stroke
Cylinder 5: –2.15 mm³/stroke
What I’ve tried so far

Swapped injectors around (e.g., cylinder 4 with cylinder 3). Correction values stayed with the cylinder, not the injector.
Also tried with a second-hand set of injectors – slight variations, but overall the same pattern (cylinder 4 always high positive, others compensating).
This seems to rule out the injectors themselves as the root cause.

Observations

Cylinder 4 always shows a strong positive correction, while others go negative to balance it out.
The ticking/clicking sound remains regardless of injector swaps.
At higher revs the sound is not audible (engine noise covers it, or it disappears).

My question to the forum

Has anyone experienced something similar with this engine?
Could poor compression in cylinder 4 explain both the correction values and the ticking sound?
What’s the best order of checks to confirm the cause without throwing money at random parts?

Any advice, shared experience, or diagnostic tips would be much appreciated!

Thanks in advance.