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TonyMax Profile
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Date Registered: 05-2014
Location: Canberra
TOTAL POSTS: 14
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T31 Diesel Exhaust Smoke


Hi,

We've had our 2010 T31 for about six months now and it has been serviced by Nissan once. At that service I asked them how much black smoke is normal for these cars as it's our first diesel anything ever.

They reset the basic ECU settings and advised that the smoke was normal for a vehicle with ~150,000km.

It's due for another service and the smoke emissions are still concerning me, sometimes while not towing but mostly while towing. The covering of black soot on the tailgate is a dead giveaway.

Most other late model diesels I see driving around don't emit the traditional diesel black smoke.

What could be the cause of excessive black smoke? EGR? DPF? Something else?

Does anyone have any suggestions on things I could do or Nissan could do to reduce the smoke emitted from our vehicle? Would cleaning the EGR valve have any effect?

Cheers in advance,


Tony

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Member no. X-3698
2010 Diesel TS
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Revhead Kev Profile
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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 5357
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Re: T31 Diesel Exhaust Smoke


Black diesel smoke is caused by an improper fuel/air ratio with the diesel not being burned properly.
Most common causes of black smoke are faulty injectors, a faulty injector pump, a bad air filter (causing not enough oxygen to be supplied), a bad EGR valve (causing the valves to clog) or even a bad turbocharger. Some of these are easy to find and fix.

Check your air filter to make sure it is not clogged. If the smoke is blue then also check the filter for oil as blue smoke usually means burning of engine oil.
Next would be to have the EGR cleaned.
Is the Xtrail down on power or the fuel consumption higher than expected ?

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Kev X450(c) T30 Guru
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Date Registered: 05-2014
Location: Canberra
TOTAL POSTS: 14
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Re:


I get pretty good power and fuel consumption, ~[sign in to see URL] towing a 500kg dog trailer and 7.x around town.

It's going in for a major [sign in to see URL] service tomorrow at which time I assume they will replace the air filter, so I'll see what it's like after that.

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2010 Diesel TS
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Charlie250 Profile
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Date Registered: 08-2012
TOTAL POSTS: 193
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Re: T31 Diesel Exhaust Smoke


My simple answer to the T31 diesel being a smoker is nonsense!

The M9R engine (made by Renault) doesn't smoke. It acieved Euro 4 compliance by being fitted with a DPF (diesel particulate filter) which specifically designed to stop it smoking by capturing and burning off the soot that appears out the tail pipe as black smoke.

If your T31 diesel smokes then it has a problem.

The EGR butterfly valve may be stuck in the open position directing exhaust to back into the engine (therefore bypassing the DPF) meaning the DPF is constantly receiving soot and requiring extra regeneration cycles.

There was a recall relating to a bad batch of butterfly valves which jammed open or closed.

If yours was purchased used, a previous owner may have blanked off the DPF.

Otherwise there is something not right.
eg. Air fuel ratio is out - This can have several causes.

If the smoke is white it could be a leaky injector(s)

T31 diesels DON'T smoke.




  

Last edited by Charlie250, 12/Oct/2016, 2:00 am


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Date Registered: 08-2011
Location: Lalor Park, NSW
TOTAL POSTS: 1663
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Re: T31 Diesel Exhaust Smoke


Hi guys, been a while hope all is well.

As for the above comment unfortunately it's not accurate and seems very confusing. The EGR system does not direct gas to the DPF.

Here's hopefully a simpler explanation. The EGR (exhaust gas recirculation) system allows exhaust gas to enter the air intake (and therefore combustion chamber). The idea is that this gas has little to no oxygen and without oxygen there is less combustion which creates lower combustion temps and reduces NOx emissions. The EGR valve is what controls how much (if any) exhaust gas is reintroduced into the combustion chamber. As a general rule the EGR will be closed during hard acceleration and open when cruising.

The Diesel Particulate Filter (DPF) is basically a mesh that captures solid pieces of soot and traps them so they are not released with the exhaust gas. This is then burnt off during high exhaust temperature driving (such as highway).

The two systems do not interact other than both are based from the exhaust. Hopefully this diagram makes it simpler to understand.
%[sign in to see URL]]--Log in or sign up to see linked image content--

You are right in the the M9R should not smoke much at all. I would be looking at
- a clogged DPF (too full to capture particulate matter); or
- a dirty EGR valve that is not fully closing and is allowing exhaust gas into the combustion chamber during hard acceleration. This would lead to reduced oxygen and unburnt fuel being expelled through the exhaust.



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Toddyh X-2048 (c)
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