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Intermittent Emission of Black Smoke.

Posted: Fri Oct 10, 2025 12:53 pm
by David_Smith2003
Greetings

This may be quite verbose, but it will provide a clearer understanding of the issue.


Acquired a pre-owned W204 - 2012 C200 CDI last year, with about 107,000 miles and a satisfactory service history. One of the tasks performed by the prior owner was a forced DPF regeneration.

Upon acquisition, a comprehensive engine and gearbox service was conducted as a precautionary measure.

The vehicle operates well and accelerates seamlessly. However, whether I am on a freeway or a roundabout and accelerate significantly. A substantial plume of black smoke is present. I accelerated many times, emitting further puffs of black smoke, until it cleared up for a few days.

I have observed that the exhaust gas exhibits a hint of unburnt fuel or oil odours.

The automobile has lately passed the MOT with exceptional results, which is quite perplexing.

Additionally, on frigid days, white smoke is emitted until the engine reaches optimal temperature. Subsequently, the white smoke dissipates.

The engine is not consuming any oil, since I have been observing the dipstick and replaced the oil and filter myself last week.

I am considering replacing the MAF sensor; but, before incurring expenses, I felt it prudent to get an opinion.

Re: Intermittent Emission of Black Smoke.

Posted: Fri Oct 10, 2025 12:53 pm
by David_Smith2003

Re: Intermittent Emission of Black Smoke.

Posted: Fri Oct 10, 2025 12:54 pm
by Hannah_Baker2000
White smoke on cold beginning is typical. It is water vapour.

The emission of black smoke during acceleration is abnormal. Connect the vehicle to STAR or iCarsoft and search for any diagnostic trouble codes.

Re: Intermittent Emission of Black Smoke.

Posted: Fri Oct 10, 2025 12:54 pm
by Sarah_Jane1980
A forced DPF regeneration is unnecessary if the system functions properly, except in cases of several short journeys that prevent the vehicle from attaining operational temperature. A partly obstructed DPF may be the origin of the emitted soot; a proficient scan tool can measure the differential pressure and soot accumulation to ascertain this possibility.

Re: Intermittent Emission of Black Smoke.

Posted: Fri Oct 10, 2025 12:55 pm
by STAR89colin
There must be an absence of black smoke entirely! Perhaps a compromised DPF is the reason for its sale.

Re: Intermittent Emission of Black Smoke.

Posted: Fri Oct 10, 2025 12:55 pm
by David_Smith2003
The white smoke is much denser than water vapour.

It is vital to connect this at this juncture. I want to bring this to A1 in Cardiff, since it is the nearest location to me.


I will provide an update whenever I get a report.

Re: Intermittent Emission of Black Smoke.

Posted: Fri Oct 10, 2025 12:56 pm
by Hannah_Baker2000
If it is white and only after a chilly start, it will be water.