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2008 GRB 20th anniversary 6 MT
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6,591 Posts
Discussion Starter · #1 ·
My wife's 120d emmits a puff of grey/black smoke when you start it up after it has been sitting overnight.

Also, during those 2-3s it sounds as if it is running on 3 or a bit rough.

Afterwards, if I switch the engine off and back on it doesn't do it and it's smooth so I am guessing it may be a leaky injector.

Can the diesel injectors be ultrasonically cleaned like the petrol ones?

Also because she doesn't drive the car hard, the first time I take it and floor it, there is black smoke from the back for 10s (provided you keep your foot on the floor for that amount of time - it is very funny to smoke bumper tailgaters :biggrin:), after that no matter how I drive it is all clear.

Is that normal?

My guess that's just carbon build up in the combustion chamber, or?

I bought this and will see if it makes a difference.

For what it's worth, the car has had the swirl flaps removed in the last service.

It also boosts fine and fuel economy is good.

I am just getting worried if it is a worn turbo, what would the symptoms of that be or do you have any other ideas what to check?

Cheers!
 

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Premium Member
2008 BMW Auto
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114 Posts
The wifes 2008 520D isn't the smoothest on start up, but then again alot of diesels are a bit rattly til they get a bit of heat in them. My old Jeep, which i'm replacing with the Foz, sounds like a bag of spanners on start up, but always has.The black soot will more than likely just be carbon build up, when the mother in law uses our car for any length of time, as she never drives over 50mph anywhere, the check engine LED on the dash usually illuminates as the DPF will be getting choked up, driving at 70mph on the motorway for 30 mins or so usually clears this up as well.
Just a thought that could it be the glow plugs maybe not the best, hence a bit rough for the 1st few seconds then ok once heat has got into them?
 

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98 sf - gls manual
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1,119 Posts
as above, the wynns stuff is ok to.

if its grey smoke aal the time i would worry, black just build up.
im on my 10 {ish] diesel and most of them are like that, even the last 350 merc did that if i poodled round in it.

and i belive?? there is a place on ebay offers a injector cleaning service??


just read that don, makes a lot of sence.
there was a garage round by me, made national news a few years back buy mixing there diesel with carosen [spelling]. that stuff is not kind to your engine after a while.
 

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2004 FSTi 6 speed manual
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2,015 Posts
I hope its not a ring gone as this can occur when you've a wee bit of piston slap , and as you said it sounds like it's running on 3 cylinders ....Mind you as its black smoke it's prob not as it's blue when your rings have gone.....Or is that just petrol ...oh idk :shake:

Hope all goes well tho bud .
Andy
 

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2006 2.5XT 5 SP Man
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1,012 Posts
if its a greyish smoke on startup I would say glowplug as its also running on 3 cylinders.

with regards to the chuffs of black I find that all BMW diesels seem to do it, as long as its not blue or white your laughing!!

might be worth you cleaning the EGR for good measure though (or blanking it off makes more sense)
 

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2015 Fiat van Man stick
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4,808 Posts
Sounds like standard diesel stuff to me. Cold start system doing its thing and black smoke when flooring it is normal up to a point.

I used to use the Forte diesel cleaner. Makes a big difference.
 

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2008 GRB 20th anniversary 6 MT
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6,591 Posts
Discussion Starter · #8 · (Edited)
How many miles has it done??

worth a read
Diesel injector cleaning | Motoring | RACQ
87k but it has FSH.
I've had a read at the article, thanks.
May be worth having the injectors checked then depending on how much this costs; I don't really want to start spending on this car unless it is absolutely necessary and plan to run it to the ground :O
It doesn't really bother me as after a couple of s the car runs fine but if checking the injectors won't break the bank I might do it.

The wifes 2008 520D isn't the smoothest on start up, but then again alot of diesels are a bit rattly til they get a bit of heat in them. My old Jeep, which i'm replacing with the Foz, sounds like a bag of spanners on start up, but always has.The black soot will more than likely just be carbon build up, when the mother in law uses our car for any length of time, as she never drives over 50mph anywhere, the check engine LED on the dash usually illuminates as the DPF will be getting choked up, driving at 70mph on the motorway for 30 mins or so usually clears this up as well.
Just a thought that could it be the glow plugs maybe not the best, hence a bit rough for the 1st few seconds then ok once heat has got into them?
It is a 2005 model so doesn't have a DPF I think.

as above, the wynns stuff is ok to.

if its grey smoke aal the time i would worry, black just build up.
im on my 10 {ish] diesel and most of them are like that, even the last 350 merc did that if i poodled round in it.

and i belive?? there is a place on ebay offers a injector cleaning service??


just read that don, makes a lot of sence.
there was a garage round by me, made national news a few years back buy mixing there diesel with carosen [spelling]. that stuff is not kind to your engine after a while.
I think I read on the bottle of the Wynns that it contains kerosene!
Isn't that used in airplanes?
Does that mean the car will fly now? :biggrin:
I did 150 miles today and the car seems to have cleared up nicely and seems to be more more economic than before, probably due to the additive I guess.
I'll see tomorrow morning how it starts.

if its a greyish smoke on startup I would say glowplug as its also running on 3 cylinders.

with regards to the chuffs of black I find that all BMW diesels seem to do it, as long as its not blue or white your laughing!!

might be worth you cleaning the EGR for good measure though (or blanking it off makes more sense)
Yes greyish on startup and black (to the point of not being able to see from the back window for a few s :biggrin:) the first time I accelerate hard after my wife has been pottering about in the car for weeks.

I believe the EGR must have been cleaned and some sort of filter changed (I can't remember its name) when the intake manifold was removed to remove the swirls flaps.

Thanks everyone for the help and if you have more ideas, keep them coming!
 

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Premium Member
2015 XC diesel CVT
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4,053 Posts
normal. Blue can sometimes be a little seepage from the valve guides but certainly nothing to sweat about.
Today's diesels are very low-compression and are more sensitive to compression/glowplug issues at cold start than you might think, but other than slight roughness or emission it's a non-issue.
 

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Emeritus Forum Staff
2015 Triumph Tiger XCx 1 Down. 5 Up.
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5,242 Posts
Need to take diesels for a good long blast every now and then to get everything up to temperature. They don't do too well if they're driven too gently or not very often. All sounds reasonably normal to me.
 

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98 sf - gls manual
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1,119 Posts
Yep gigsy. i agree. Had a 500 mile day out yesterday. The company focus is runing the best it ever has :)
 
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