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maf problem ?? black soot under load


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so im still having problems with my 2.0d cat. and smoking underload. ive pin pointed it down to smoking underload between 1500 and 2500rpm .. ive done the test with disconnecting the maf and seeing if anything changes but it still smokes badly and also doesn't throw up any fault codes


list of things done :

egr , inlet and intercooler clean

egr blank with 4mm hole

egr to intercooler hose boost leak fix


ran on v power nitro diesel for 2 months with eco millers fuel additive in every tank

new injectors and fuel pump and fuel filter 8 months ago by previous owner.


could this be the mass air flow metre knackered ? im trying to pin point the problem with out spending big money

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Soot built up in the exhaust which is burnt off when a load of hot gases are thrown down the exhaust. Usually happens when the engine is driven gently for a while then hard acceleration.

Regeneration shouldn't produce a lot of smoke though. It should happen at very high temperatures, which lead to relatively clean combustion of the stored soot - it's not simply belching out of the back.

As mentioned before it's basically just that diesels run a much richer air-to-fuel ratio than petrol engines and also the chemistry of diesel combustion lends itself more to particulate production.

Modern engines have got a lot better, principally because virtually all now have diesel particulate filters (the matter trap that collects the soot mentioned above) and this acts like a giant tea-strainer in the exhaust, physically trapping the soot. You ideally want a steady state with a reasonable amount of gas flow to regen, so the ECU recognises this state - ideally on a long motorway cruise - and post-injects to dramatically increase the temperature in the exhaust to about 1500 deg C mid-brick.

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