2006 1.9 TDI - P0299

[sttr]

Hi everyone.
I am still trying to earn my way onto the technical part of the forum...

I just got a 2006 caddy with the BLS engine.
It has intermittent limp mode problems and report P0299.

So this error code is related to underboost and probably have something to do with vacuum, wastegate, N95 or the turbo itself.
I have ordered a VCDS but have not received it yet.

While I wait for the stars to align and my forum access to granted and my diagnostic tools to arrive I wanted to ask you folks this:

First some symptoms.
I can drive the car just fine but if I floor it uphill in 3rd gear it will go into limp mode (glow plug icon starts blinking) until I turn off the engine and start it again.
Some times this causes the check engine light to come on but not always.
I use a cheap ELM327 to clear the code from time to time.

The previous owner (I presume) obviously mucked about in the engine bay and managed to connect the vacuum lines to the N95 valve wrong.
So the Vacuum and turbo lines were cross connected.
I have fixed this faulty connection and cleared the code but the problem persists.

So my question:
Would the fact that vacuum was connected to the boost/turbo side of the N95 valve cause permanent damage to the valve?
Is there any way to test the valve for correct functionality?

Any other tips on what can cause my intermittent limp mode?

(ok so this was 3 questions.... This happens alot to me )

[MillerTime]

One thing to check would be the vacuum with a gauge.


Sent from my iPhone using Tapatalk

[Doc]

A look on the VCDS (Ross-Tech) site brought up some information HERE, look at the bottom where a guy had a vacuum leak on a caddy and submitted a photo of the problem location.

I think the N75 valve itself is quite resilient so shouldn't think the pipes being on wrong will have caused any harm.
You say the limp mode is intermittent so the van does boost? That would be enough to say the N75 is OK.

The turbo does not have a wastegate, rather the boost is regulated by variable vane geometry controlled by the N75. The turbos do sometimes suffer from carbon deposits blocking this vane movement and causing the problem you have or sometimes overboost where the turbo does not shut down fast enough.

[sttr]

One thing to check would be the vacuum with a gauge.

This was on my list.. I just need to get hold of a vacuum gauge first.

A look on the VCDS (Ross-Tech) site brought up some information HERE, look at the bottom where a guy had a vacuum leak on a caddy and submitted a photo of the problem location.

Nice find. Thank you.
I will check this as soon as I get hold of the equipment.

I think the N75 valve itself is quite resilient so shouldn't think the pipes being on wrong will have caused any harm.
You say the limp mode is intermittent so the van does boost? That would be enough to say the N75 is OK.

Yes the van does boosts nicely until it cuts into limp mode.
The difference is quite noticable.
I will consider the N75 good for now then.

The turbo does not have a wastegate, rather the boost is regulated by variable vane geometry controlled by the N75. The turbos do sometimes suffer from carbon deposits blocking this vane movement and causing the problem you have or sometimes overboost where the turbo does not shut down fast enough.

Is there any way to test if the geometry of the vanes behave as they should?
Or is open surgery the only way?
The engine bay in these things is not really that roomy.
And I believe the turbo is integrated with the exhaust manifold.
What does it take to remove the turbo/manifold?
Is it possible in a normal driveway situation or do I need to lift the van and drop the thing down?
I am crossing my fingers that someone in here has done this procedure and did a writeup.


Thank you both for your feedback.

[Doc]

I don't think anyone has done a write-up on removal of the Turbo but if you're capable enough to even attempt it I'm sure you'll work it out.
To check the vanes I've seen a guy use a vacuum tool to gently increase/decrease the vacuum pressure and watch that the actuator moves progressively and doesn't stick/jump.

[p1andy]

Id be going for a vacuum test on the actuator. Sounds like the same symptoms i had which after checking the vacuum on the actuator the diaphragm was knackered. New actuator fitted and all has been well ever since.

[sttr]

Id be going for a vacuum test on the actuator. Sounds like the same symptoms i had which after checking the vacuum on the actuator the diaphragm was knackered. New actuator fitted and all has been well ever since.

This is very interesting ..
I am getting a vacuum tool this afternoon and will be checking this in particular.
The crossconnection I mentioned earlier also applies to the actuator.
Every part of the vacuum system after the N75 was affected by this fault.
As Doc said in his post the valvecover is also a part of this system and was as such also put under false vacuum for who knows how long.

If the vacuum lines from the boost output of the N75 holds vacuum with no leaks the next test will be this actuator.
What should expect to see?
Is there any moving parts that will correspond to increased vacuum?
I have never worked on a VW engine before and the little turbo experience I have did not have a variable vane actuator but a wastegate.
A video of a working unit would be very helpful...

Where can I get a replacement If the diagnostic ends with a broken diaphragm?
Is it a big job?
Did you do it yourself or did you leave your van with a mechanic?



edit:
Found this: https://www.youtube.com/watch?v=Ppif4qC560U
Maybe relevant?

[Dugpal]

My dad had this issue on his old polo. He ended up swapping some pipes round to the vacuum unit (is this the n75 valve?) And it fixed the issue.

Not saying itll fix yours but you mentioned they have been swapped around so it sounds like the issue lies in this area!

[p1andy]

When you apply the vacuum tester to the actuator pipe you should see the stem of the actuator move. Also it should hold the vacuum. On mine the actuator stem didnt move much and the vacuum bled off instantly so knew the diaphragm was knackered.

Replacement actuator was about £40 from Darkside. The job is pretty simple but its a sh!t of a place to get to with it in situ. I am fortunate to have small hands so managed to get in about the two retaining bolts and the two nuts holding the actuator.

When you fit the new one, you have to set the preload on the actuator by screwing the retaining nuts to a position where it moves at the desired vacuum. Cant recall what the value was off top of head.

Give yourself an afternoon for it, good long flexi magnet is always good to have for picking up the nuts when you drop them trying to remove/install them

[sttr]

So...

I got a vacuum "gun" pump thing.
I can build vacuum with it and it has a gauge that show how much vacuum is registered.
The good news is that the entire vacuum system produseres about 23 in/hg on idle which I understand is within reasonable.
I also tested the output of the n95 valve and pumped vacuum from the components that are attached on the boost output of the n95.
it seems to hold its vacuum while I twisted and mistreated the vacuum hoses to see if one of them was bad.
All good.

Then I got to the next test that Plandy suggested.
I applied vacuum directly to the vnt actuator.
It holds vacuum, but the stem does not move.
So either the actuator is frozen or the vnt control-ring is seized... Probably.
The problem is that it is really, Really, tight in the back of the engine bay. I cannot see how to access any of this unless the manifold with the turbo and the actuator is removed from the engine.
But I fail to see how there's is space to actually remove it....
Is it really necessary to lift the engine out to get to these parts?
I hope not...

While typing this I think if one more test I can do before I must commit to "open heart surgery"
While applying vacuum to the actuator there was a inline-oneway-valve between my vacuum tool and the actuator. In theory this could stop the actuator stem from moving back and it was already maxed out when I observed it.
I need to check if the vacuum lines with their one way Inline valves are mounted correctly.

Does anyone have a map or a diagram that shows these details on a BLS 1.9 tdi?

I'm crossing my fingers!
Also if you think I have missed something or have misunderstood how this is supposed to work I would appreciate your thoughts on this.

[sttr]

update

I finally found a vacuum diagram for a tdi engine with BLS engine code.
Its from a Octavia manual but that shouldnt matter much.
Clicky

This shows that the "inline check valve" I was refering to in my last post shouldnt be there.
And even worse.
The VNT actuator is the only thing connected to the boost output of N75 valve.
This is not the case in my engine.
Previous owner really f. this up.

As it stands right now the vacuum line to the actuator goes to the T-connector (more like a W, it has 3 prongs) that also goes to the valve cover of the engine.
The checkvalve should not be there at all, but between the "W" connector and the vacuum pump.

Geez....
I know what I must to after work today.


edit:

Could'nt wait.
Did a engine dive during my lunch break.
Switched the vacuum hoses over according to the linked diagram and went for a test drive.

Schweeeeet
All good. happy days.

P0299 - Underboost intermittent problem fixed by doublechecking that vacuum is ok (no leaks) and that the hoses are connected to their correct position!

[foneflex]

hi, sorry to pull up an old post, i have the same issue i think, i can clear the engine mal light but it comes on a couple days later
i thought at 1st it was the N75 valve which i changed it drove a bit better for a day the eng ine mal light came on again and seem down on power again

looking at the Octavia drawing you have put the link to, did you swap the 2 bigger hoses around? as 1 of those hoses goes to the air intake ?

i will check this tonight on mine but cheers for creating this post its been a good help so far

[R1rider]

Hi, did you resolve your issue? I've just dropped mine into the garage to let them look at the same issue. Mine will get toaround 50 mph get a little judder and then take 20 mins to get to 60 (well feels like it) eml will light up with p0299 code given. Strange thing is though on odd occasions it drives like I stole it and no issues whatsoever, see if lads at garage can find anything out the ordinary with it.

[foneflex]

Hi sorry just seen your reply, it has got a lot better, turns out the egr pipe was leaking so it has now been fitted with a dark side egr delete, did you get yours sorted ?