C5 X7 16 2L diesel, the airdoser and EGR valve movement

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belaprops
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C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by belaprops »

I have posted a few questions about my lovely C5 x7 16 2ltr, and have learned a few things, but still not found the fault. I'm really thankful for this

Can anyone give me a confirmation on what moves at start up of the engine so I can rule out a few parts.

When the engine starts the vacuum system will make the airdoser valve move, I clearly see it contract and after a few seconds release again.

The other valve which is fixed on the front of the EGR should move because I know there is a voltage present at the solenoid which controls this valve. But it's not moving. I bench tested this valve and it works at 7.5v, the car shows 9v at startup.

It also seems that the airdoser valve solenoid when not active is open to the exhaust of the vacuum, meaning that only when this solenoid is active the vacuum will be working on the other two in the system.
I tested this new one before I replaced and it was not fully closing, do we need to adjust these new from the citroen spares box

So i presume these all work in series with each other. Saying that when the airdoser is active, the other 2 can work of the vacuum. Makes no sense to me, but I'm not a engine expert .

If anyone can tell me if the EGR valve moves when the engine is started, then that gives me a starting point to check if it all is working properly. I might not be right calling it the EGR valve, but it controls a spigot on the EGR which moves freely. I presume there is not a second valve on this EGR module.

I figured out that the if the airdoser closes fully the engine stalls, makes me think that EGR is not open to compensate for the lack or air coming in.

As for different names and confusion therefore, where is the turbocharger boost control position sensor located, because that is a confirmed fault. I did do the full temp and motorway drive , but it does not clear .

Thanks for you help in advance again, I will get this engine perfect again.

belaprops
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by belaprops »

Somehow, the functionality of the airdoser valve came back and the valve on the EGR started to work.
Now I have the the engine revs occilating when I keep a steady foot on the accelerator.

Not sure why this just appeared

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KennyW
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by KennyW »

Bela,

Can you get some live data with the engine running ie showing the injectors etc, it's possible some carbon has found its way into the injectors through the egr recycling process.

Any other relevant data would be helpful.

Kenny

belaprops
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by belaprops »

I have torque but not sure how to do that.

Stationery I found a definite jumping of the revs at around 1200 to 1800 , revving up or down by about 200 I think.
When idle at 800 it's fine ,and when close and above 2000 is ok, still have power from the engine, but when driving at lower revs it also happens.

It started after miraculously having the two actuators starting working again. The airdoser is mostly closed, just enough not to stall the engine and the EGR (I presume it is ) is also retracting now, which did not happen before.

I have a video clip of the two while the revs were jumping

belaprops
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by belaprops »

As the engine seem to be running fine above 2000 revs I might think it's something related to the air doses, when I'm between 1500 and 1800 revs it has jerks holding back the revs,
Why would the valve in the airdoser suffocating the engine. When static and slowly increasing the revs at 1500 it starts dropping the revs , same at 1800. I can't upload the video showing this.

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KennyW
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by KennyW »

Have you taken the doser off to check the state of the flap ?

Is it sticking slightly thus causing the airflow problems ? This may register as a fault.

Have a look at the previous fault codes to see if there was/is one.

Otherwise I'm stumped.

I have the same engine but don't have this problem.

Kenny

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GiveMeABreak
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by GiveMeABreak »

belaprops wrote:
08 Jun 2020, 15:56
As the engine seem to be running fine above 2000 revs I might think it's something related to the air doses, when I'm between 1500 and 1800 revs it has jerks holding back the revs,
Why would the valve in the airdoser suffocating the engine. When static and slowly increasing the revs at 1500 it starts dropping the revs , same at 1800. I can't upload the video showing this.
2 reasons: (1) first for the cut off function below, but more to the point, see point (2).

Role of the double mixer with position repeat sensors:
  • To monitor the inlet pressure so as to optimise the exhaust gas recycling (EGR) rate
  • To prevent air from passing into the inlet circuit when the engine is switched off (cut-off function)
  • To regulate the temperature when the particle filter (FAP) is being regenerated
(2) Exhaust gas recycling
The high temperatures, caused by the excess air combustion mode proper to diesel engines, produce a large amount of nitrous oxide (NOx).
The admission of exhaust gas into the combustion chamber reduces the quantity both of oxygen and of nitrogen present at combustion.
The temperature of combustion is then lessened, which reduces the amount of nitrous oxide (NOx) emitted.
Some of the exhaust gas is diverted into a duct linking the exhaust to the air intake.
This duct is closed by an electric EGR valve.

On the command of the engine ECU, the electric EGR valve opens, giving the exhaust gases a controlled access to the inlet manifold.
N.B. : Too large a quantity of recycled exhaust gas causes an increase in emissions of soot, of carbon monoxide (CO) and of hydrocarbons (HC) by reason of poor combustion due to lack of air.
In addition to opening the electric EGR valve, the engine ECU orders the air mixer to close partially.

The closing of the air mixer causes:
  • A vacuum in the inlet manifold, drawing in the exhaust gases
  • A diminution of the amount of air entering

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KennyW
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by KennyW »

Marc,
On Bela's engine it is the single air doser where as mine is fitted with the double unit but only utilising the one valve, I think it is the hot air valve.

I have not seen any tech details for this or the single airdoser valve.

Kenny

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GiveMeABreak
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by GiveMeABreak »

It's just what is included for the system fitted to the DW10CTED4 engine Kenny, I know they made some changes - but I'm struggling to find more detail, but I'll keep looking.

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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by GiveMeABreak »

Ok, so apparently, on the DW10C engine, the by-pass function is not active, the hot air (by-pass) flap is only activated in the event that the cold air (mixer) flap seizes.

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KennyW
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by KennyW »

Marc,

Looking at the the parts diagram for Bela's DW10, I presume it is the cold air mixer since the piping runs from the turbo to the air cooler and into the air doser

[attachment=0]Turbo air piping.jpg

Could this be sticking causing her engine to rev between 1500 -1800 rpm.

Kenny
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Turbo air piping.jpg

belaprops
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Re: C5 X7 16 2L diesel, the airdoser and EGR valve movement

Unread post by belaprops »

I have been searching more abd on the FB group of the C5 they have mentioned that it might be something else.
The constantly closing airdoser has stopped , there might be another thing causing it.
Now p2562 is confirmed and tge suggestion is there could be a vacuum leak so it cant reach the presure to controll the turbo vanes. Or that the vanes are sticking due to carbon deposit.
The solenoid of the turbo , as i understand is the middle one , is getting hot, which indicator its always engaged.