GTD- help with engine issues?

[Bigwinn]

Hi all

First time poster; full disclosure I am a self confessed Bimmer geek so don't hold that against me eh?

Now this is the missus car. Bought it after I had a 63 plate GTD which I loved as a company car. All in good order apart from a niggle I need your advice with- as I am handy with the spanners I am confident to get into stuff myself but also not knowing VAG stuff AND forced induction stuff I would appreciate your views...

2015 GTD with 125k miles.

Issue happens when accelerating hard/giving it beans; car goes into limp mode and throws P0299 over/under boost error.

Also general driving I'd say the car is down on power especially boosting in 3rd and 4th. MPG seems low too.

Did the usual checked for leaks/obvious hose issues etc, nothing immediate. Took it to my local VAG specialist and his more detailed OBD showed nothing more so he looked for leaks too.

He suggested as nothing obvious to change the diverter valve which I have done, do difference (other than the error seems to happen more often than it did before??)

So I am starting to lean towards looking at the turbo actuator to see if thats slow/fouling? Are there any how to guides how to check this?

I've replaced the distribution value and the MAP sensor. No change

What else would you guys suggest I look at?

Anyone experienced similar?

Cheers!

Stuart

 

[Bigwinn]

Today I got the car code free then took it for a spin to recreate the limp mode fault P0299

Screenshots from VCDS attached- what do you see that could lead me to a solution?

Cheers

Stuart

 

[Bigwinn]

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• Bigwinn
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• Bigwinn
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[adjat84th]

When you say diverter valve, do you have a pic of what you replaced? The diesels don't have that part that the gassers do.
In your pics though:
It's way underboosting in your fault code specifics, 2770hpa requested and 1470hpa actual with 55% duty cycle on the actuator.
At idle and in the adaptation menu, run an "adaptation of the turbocharger" with VCDS. That will fully cycle the actuator while you watch under the hood. I'd check that it's moving fully up and down when VCDS runs the test, exhaust note will change while doing this. I'd also pull the vac line off with the car off, and check that when under vacuum it holds steady and doesn't leak. A leaky actuator would underboost.
Also, apply vacuum to the lines from the actuator and the N75 to make sure they're all leak free as well.

 

[Bigwinn]

Superb- thats what I am thinking but wasn't sure how to test- I will give that a blast on VCDS now

The part I changed was a pressure converter- simple like for like swap

 

[adjat84th]

You replaced the MAP sensor? Or maybe it's the N75 that's up on the firewall that you changed?

 

[Bigwinn]

thats the one the N75

 

[Bigwinn]

Just ran the adaptation test

finished 'successfully' but I didn't run any monitors while doing it

I could see the armature moving back and forth and the turbo making low noises

Are there any monitors I can run when doing a test?

 

[adjat84th]

The turbine actuator position feedback should go from 99.99% to 10 or maybe even 0%. If you can't look at that during the test, you can simulate it with a vacuum pump attached to the actuator and the car off but ignition on. No vacuum at all should read close to 0% I believe, and full vacuum (arm hits the stop) should be near 100%
Can also check that it's holding vacuum when doing that.

 

[Bigwinn]

The turbine actuator position feedback should go from 99.99% to 10 or maybe even 0%. If you can't look at that during the test, you can simulate it with a vacuum pump attached to the actuator and the car off but ignition on. No vacuum at all should read close to 0% I believe, and full vacuum (arm hits the stop) should be near 100%
Can also check that it's holding vacuum when doing that.

Thanks I'll have a go in the morning

Based on what you see do you think thats a boost leak or actuator fault?

 

[pedroYUL]

Check measuring block 43.2 (2nd field on measuring block #43). Key on, engine off should read zero or close to it, and engine running should read close to 100:

 

[pedroYUL]

But most important is the difference between engine running, and just key on should be real close to 100.

 

[Bigwinn]

Check measuring block 43.2 (2nd field on measuring block #43). Key on, engine off should read zero or close to it, and engine running should read close to 100:

Thanks bud will have a look this am

 

[Bigwinn]

But most important is the difference between engine running, and just key on should be real close to 100.

I can’t use measuring blocks- it’s blanked out?

 

[adjat84th]

I use the advanced measuring blocks, and the turbine actuator position is the same metric Pedro is referring to.
If the actuator holds vacuum, I'd then look at the charge pipe connections for a boost leak...there aren't many of them on these so should be easy

 

[Bigwinn]

I use the advanced measuring blocks, and the turbine actuator position is the same metric Pedro is referring to.
If the actuator holds vacuum, I'd then look at the charge pipe connections for a boost leak...there aren't many of them on these so should be easy

whats the best way to check it holds vacuum?

pop the pipe off and apply a tester?

as I’m not a forced induction guy, where should I look in the charge pipe connections?

cheers

Stuart

 

[adjat84th]

Feel for any oily spots along the piping that goes from the turbo to the charge cooler (pull the airbox for access). The plastic pipe can get brittle over time. You'd likely hear this big of a leak I would think even at idle while listening under the hood though.

Pull the vacuum hose off the actuator, apply vacuum until the arm stops, let it sit, if it holds steady then it's not leaking.

Outside of these, maybe pop over to Darkside for some help. They'll figure it out in no time, and not throw parts at it.

 

[Bigwinn]

Feel for any oily spots along the piping that goes from the turbo to the charge cooler (pull the airbox for access). The plastic pipe can get brittle over time. You'd likely hear this big of a leak I would think even at idle while listening under the hood though.

Pull the vacuum hose off the actuator, apply vacuum until the arm stops, let it sit, if it holds steady then it's not leaking.

Outside of these, maybe pop over to Darkside for some help. They'll figure it out in no time, and not throw parts at it.

What’s Darkside? Sorry for the dumb questions!

 

[adjat84th]

Darkside Developments is a performance shop but does plenty of jobs like this. Google them, they're a supporting Vendor here as well. Good folks, maybe an hour drive from you?

 

[Bigwinn]

Nice one that’s great

 

[pedroYUL]

I can’t use measuring blocks- it’s blanked out?

Do you have just VCDS lite (clone hardware) or full version?

 

[Bigwinn]

Full I thought!

 

[pedroYUL]

Then you should have no problems with measuring blocks. The one I mentioned relates to how the actuator position sensor "sees" the rod.

If the difference is less than 100% it will throw a code

 

[Bigwinn]

A quick view please

Could this be a full DPF causing the issues?

Recirc failed on VCDS, boost impeded?

 

[pedroYUL]

Look up the error code in the VCDS webpage, it sometimes tells you how to start troubleshooting.

That code is related to the turbo actuator/position sensor/VNT mechanism... that's where you should look, not DPF

 

[FJBGTD]

To check your DPF values use vcds engine/adv measuring, in the search box type particle, tick the boxes for soot mass, 20 or under is ok, 20 - 30, you need a regen and to drive at over 40 mph at steady revs around 2k. You can see when the car is regenerating as the stop start is not available, so on the infotainment go to the car menu and select stop start, if you see engine must be running it is in regen mode, once it returns to active it has finished. If the soot is over 30 do a forced regen, you should find instructions on the ross tech website.