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I've been chasing an engine issue for over a year but I'm now at the end of the road.
Originally, I'd occasionally get zero boost when putting my foot down, or a severe kangarooing and the car would just hold gear and rev, this threw codes for back pressure sensor, changed this and it made no difference.
So over time, I have replaced:
Batwing intake (flange was cracked)
MAFS (air mass fault)
PCV (internals were screwed)
Turbo actuator (this threw a code originally, hence changing for reconditioned unit, not a Chinese one)
Back pressure sensor
Fuel pressure regulator
Injector leak off pipe (snapped accidentally)
Glow plugs (2 threw a fault so replaced all of them)
Gearbox service
Regular service
EGR valve (sticking valve)
Finally, when changing the EGR valve, the issue went away, however, the new EGR introduced low speed acceleration fluttering.
I put the old EGR back in (after cleaning), new problem went away instantly, old problem came back.
The slow speed stuttering with the new EGR doesn't throw any codes at all
The issue goes away if driven hard, it's just creeping in traffic, slight inclines or turning corners that really highlights the issue.
I can read live parameters, but not entirely sure what to be looking for with this as the lack of code being thrown isn't giving me anywhere to start investigating
Edit* have just noticed a lot of black smoke from the exhaust as well, thick black smoke on acceleration...but there is a tank of fuel diluted with a carbon cleaner in her at the moment
Thanks for any help
Last edited by Shaggy1988; Oct 16, 2025 at 01:02 PM.
When was the fuel filter last changed? Likewise the air filters?
This car ran, but was hesitant and felt down on power, not surprising, and idle was erratic. Changing the air filters and fuel filter made a significant improvement. It still hunts a bit at idle, (my R350 CDI was the same, so possibly a quirk of the V6 diesel), but no driveability issues. It's also smokey if left idling, but a spirited drive soon clears it up.
Incidentally, mine is an '07 ML280 CDI with no Adblue or DPF and 205k miles.
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