White smoke when full throttle in neutral

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berdza
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White smoke when full throttle in neutral

Post by berdza »

Hi guys, I need your help because i don't have the slightest idea where to start looking for cause of this.

I own citroen c5 2005 1.6 hdi 110hp. The car is having problems with activating turbo so i tried to check my wastegate.

I put it in neutral and stepped on gas to see if the wastgate would move, and the car had problems going over 3500rpm. RPMs were jumping up and down and then i stepped on gas all the way and it went to 4500rpm, but there was a lot of white smoke(Only when full throttle in neutral. NOT while driving) while i was doing that and I heard almost like a pop or two like the car was missfiring.

It drives ok, no white smoke but it does not accelerate as before(the turbo is not boosting but its problem for another time)
  • *I had the injectors tested 12 months ago, all were fine but they were leaking a bit of fuel and mechanic didn't see it while testing injectors, so he said its small amount.
  • fuel filter replaced 12mo ago
  • oil changed 2000km ago
Diagnostics only show underboost fault

Thanks in advance.
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MattBLancs
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Re: White smoke when full throttle in neutral

Post by MattBLancs »

First off, the 110 bhp 1.6 HDi does not have a wastegate. It is a VNT turbo and what looks like a wastegate instead is moving the vanes within the exhaust housing.

Reving an engine in neutral does require any significant amount of power (as only the engine internal friction to overcome) hence would not expect any significant boost to be required or generated.

Should have no issue touching 5,000 in neutral (well it should on the move, can't think I've ever revved it to redline in neutral because, well due to mechanical sympathy!)

Lots of white smoke= cold engine? Suspect predominantly steam not smoke as will condense in cold exhaust system.

"Problems activating turbo" and "turbo is not boosting" = I'm not sure why you don't think these are linked??
berdza
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Re: White smoke when full throttle in neutral

Post by berdza »

Before everything i would like to thank you for your answer.
MattBLancs wrote: 01 Aug 2023, 20:40 First off, the 110 bhp 1.6 HDi does not have a wastegate. It is a VNT turbo and what looks like a wastegate instead is moving the vanes within the exhaust housing.
I understand that, I don't know what is the "wastegate" called in that case, where i come from its called doser. But i checked the rod that is pulled by vacuum tube and the rod moves easily so the flaps are moving.(I pushed it down and pluged the hole where air gets in and membrane held ok when i unpluged it the rod went back up)
MattBLancs wrote: 01 Aug 2023, 20:40
Lots of white smoke= cold engine? Suspect predominantly steam not smoke as will condense in cold exhaust system.
Nope the car was running for myb 30mins. and i only had power at 3500+ rpm(i usually felt the car starting to pull hard arround 3000rpm)
But the white smoke was huge and it smelled like fuel(not thick but it was all over the place and it went 3-4m up) and it was hot outside.
MattBLancs wrote: 01 Aug 2023, 20:40
Should have no issue touching 5,000 in neutral (well it should on the move, can't think I've ever revved it to redline in neutral because, well due to mechanical sympathy!)
I have never revved it more than 4500rpm. But the car just started bouncing on its own from 3000-3500rpms even though i held my foot at one place(cca 70% throttle ). Idk why it would do that in neutral.
MattBLancs wrote: 01 Aug 2023, 20:40 "Problems activating turbo" and "turbo is not boosting" = I'm not sure why you don't think these are linked??
How are they not linked. If the turbo doesn't activate it does not boost,but as I said its a problem for another time. I will get it looked at. But my main problem is that white smoke(and i don't think its oil).
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Rp0thejester
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Re: White smoke when full throttle in neutral

Post by Rp0thejester »

Possible EGR valve? Just throwing it out there as only time I've ever seen anything revving up and down with a bit of smoke out the back was when using EGR cleaner whilst keeping the throttle at a set position
Ryan

'99 Xsara 1.6 X (Red) with Sunkissed bonnet. T59 SBX
'54 Astra Estate 1.7DTI (Artic White)
'06 C8 2.2Hdi Exclusive (Aster Grey)

Champion of Where's CitroJim :-({|=
Yes I ask the stupid questions, because normally it is that simple.
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MattBLancs
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Re: White smoke when full throttle in neutral

Post by MattBLancs »

Hi again,

Terminology: I think "VNT actuator" is the name to use.
There is an "air doser" - but this is the unit on the turbocharger outlet pipework and bypasses the intercooler when required (warm up and DPF regeneration)

Engine warm so less likely to get steam: ok great, thought best to check, rule out the simple stuff first.

VNT actuator moves under finger pressure and seems to hold vacuum (so diaphragm intact) = both good news.

Think we are both in agreement turbo actuation linked to turbo not boosting - just a misunderstanding.

For clarity, can you describe the driving performance issues you're experiencing, just to be clear on "how does it feel?"
Thanks,
Matt
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MattBLancs
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Re: White smoke when full throttle in neutral

Post by MattBLancs »

Rp0thejester wrote: 01 Aug 2023, 21:52 Possible EGR valve? Just throwing it out there as only time I've ever seen anything revving up and down with a bit of smoke out the back was when using EGR cleaner whilst keeping the throttle at a set position
Like the train if thought - more generally, reving up and down for a diesel engine ultimately is "more fuel = rev up, less fuel= engine slows down"
EGR cleaners are volatile solvent type things (I.e. no trouble burning that!) So can see why that makes the revs climb :)
Last edited by MattBLancs on 01 Aug 2023, 22:02, edited 1 time in total.
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Rp0thejester
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Re: White smoke when full throttle in neutral

Post by Rp0thejester »

It did on my C8, scared the life out of my boy. Just thought I'd mention it, anything that can be discounted is a good thing
Ryan

'99 Xsara 1.6 X (Red) with Sunkissed bonnet. T59 SBX
'54 Astra Estate 1.7DTI (Artic White)
'06 C8 2.2Hdi Exclusive (Aster Grey)

Champion of Where's CitroJim :-({|=
Yes I ask the stupid questions, because normally it is that simple.
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MattBLancs
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Re: White smoke when full throttle in neutral

Post by MattBLancs »

Stuck EGR (valve open all the time or not closing fully when it's supposed to be) tends to be poor performance at times when the engine is hungry for air (power demanded) and it gets a gob full of exhaust gases instead. As you say, can give smoke too as engine squirts in diesel that can't find enough oxygen to burn = smoke from poor combustion.
berdza
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Re: White smoke when full throttle in neutral

Post by berdza »

MattBLancs wrote: 01 Aug 2023, 21:55 For clarity, can you describe the driving performance issues you're experiencing, just to be clear on "how does it feel?"
Thanks,
Matt
Well i drive my car sometimes a bit faster. 2 weeks ago i drove it on a highway at arround 185kmh for a minute or two. It drove great. I drove for 15-20 mins after that and turned it on and off a couple of times. Started heading home and overtook 3 cars but I pressed full throttle at low rpms(2000)
all of a sudden system deplution faulty error pops up and the car is in limp mode. Turn it on and off and it runs ok no problems but check engine comes up. I go to mechanic and he says "I had the same car, when u go full throttle at low rpms, turbo underboost fault comes up" so he errased faults and car was again running great(when i say great this is what i mean: it pulls kind of slow until 3000rpms and then starts pulling really good and dumps a lot of black smoke)

NOW: it pulls slow until 3500rpms and then gets a little kick and pulls a bit better but there is no black smoke anymore.

DPF should be clean(filled the aditive 6mo ago, and it is not driven in urban area only. I often go for 200km trip and floor it from time to time)