Excessive exhaust smoke

[minyak]

Hi there,

Recently, I noticed unusual excess exhaust smoke (black/greyish in colour) being emitted from my tailpipes. I own a 100K mile C220 CDi (2001 W203 Model). This has never happened before. The car has a been regularly serviced as well. The smoke appears when the engine is at normal operating temperatures and when I come to a standstill (say at a traffic light or junction) whilst the gear is in D position. On the move it seems fine though. No fault messages are being indicated by the on-board computer and the engine still performs as normal, no loss of power, misfiring, etc. Could it be the injectors are faulty (i regularly used Redex btw), or fuel pump delivering too much fuel for some reason, or lack of oxygen for clean combustion. Any ideas anyone?? Cheers.

 

[Dieselman]

Whilst it could be the injectors it is more likely to be either the EGR valve sticking or the MAF sensor going South, causing over fuelling at idle.

Try disconnecting the MAF sensor and see if the smoke goes away, also you should be able to check the EGR valve by sucking on the vacuum pipe.

It would be worth pulling the acoustic cover off the engine and ensuring there is no combustion leakage around the injectors as that would have the greatest effect at idle, when pressures are lower.

It shouldn't be the pump as on a CR engine it pumps equally all the time and timing control is a function of electronic injector control, not pump controlled.

 

[jgevers]

Whilst it could be the injectors it is more likely to be either the EGR valve sticking or the MAF sensor going South, causing over fuelling at idle.

Try disconnecting the MAF sensor and see if the smoke goes away, also you should be able to check the EGR valve by sucking on the vacuum pipe.

It would be worth pulling the acoustic cover off the engine and ensuring there is no combustion leakage around the injectors as that would have the greatest effect at idle, when pressures are lower.

It shouldn't be the pump as on a CR engine it pumps equally all the time and timing control is a function of electronic injector control, not pump controlled.

And if the above don't make a difference, visit a dealer or a Bosch garage to check the injector efficiency. This can be done with diagnostic computer and measuring the amount of diesel from the leak-off pipes.

Cheers

 

[minyak]

Oh cheeers for the info. Will be having these items checked at the specialists pretty soon. Will let you all know the outcome asap.