2.0 TDI 170HP BRD power loss (boost or vacuum leak?)

[Diggy98]

Hello guys, I'm seeing that my 2.0 170HP quattro doesn't always "pull" like it should. There are days when it runs sweet and really feels like 170hp and days when it seems to be losing some power with no reason. No check engine or other lights and no errors show up. I don't have any good mechanics in my area so I was hoping that you could help me try to diagnose the problem myself...Thanks in advance!

[Steve Q]

Hi Dragos, when my sister had a similar problem with her golf mk4 diesel it transpired that some of the vains/blades within the turbo had broken off which caused the loss of pulling power. To resolve this she had to have a new turbo. 

What's the mileage of your a4? 

Cheers

Steve 

 

[Diggy98]

  Hello Steve, thank you for your answer! The car has 260 000 km (not miles :D) on the clock but the turbo was replaced 10 000 km ago with a professionally refurbished one. I know that this doesn't mean that it couldn't be the turbo (mistakes are human), but sometimes (like the last three days) it pulls like a crazy. That's why I excluded it.

  My next move is to try and replace all the little vacuum hoses as they don't cost a fortune and are known to cause problems that are similar to mine, so I would be grateful if someone could help me with some dimensions (i can't find them anywhere). Thanks!

[Steve Q]

Well like you say you hope it's not the turbo as it's just been refurbished but I'm assuming you have some form of warranty with it? 

Replacing the pipes is a good idea as they do have a history of leaking at the seals/joints. I've had a look for part numbers and I've attached 3 eBay links for info. They show you the picture of the part and the part numbers. Here you are: 

https://m.ebay.co.uk/itm/AUDI-A4-B7-1-9-2-0-TDI-INTERCOOLER-TURBO-HOSE-PIPE-04-08-8E0145790P/222628764277?hash=item33d5b55a75:g:DMMAAOSwH35Zpqr6

https://m.ebay.co.uk/itm/AUDI-A4-B7-2-0-TDI-2004-07-INTERCOOLER-PRESSURE-HOSE-LOWER-LEFT-8E0145837G/222556316237?epid=1128397811&hash=item33d163e24d:g:7LAAAOSwrfVZTRWS

https://m.ebay.co.uk/itm/AUDI-A4-B7-2-0TDI-TURBO-INTERCOOLER-HOSE-PIPE-8E0145790P-8E0145790D-NEW/291709798478?hash=item43eb42484e:g:7sAAAOSw-3FZJr8D

https://m.ebay.co.uk/itm/AUDI-A4-B6-B7-A6-1-9-2-0-TDI-Turbo-Intercooler-Hose-Pipe-8E0145834AR/321812914027?hash=item4aed8b5f6b:g:BEUAAOSwhvFZHXDf

Doubt these are all of the pipes but the part numbers and info maybe useful.

Have you had a diagnostic check done to see what fault codes (if any) flag up? 

Hope IV helped :) 

Cheers

Steve

[Diggy98]

I really appreciate your help, Steve! Obviously the turbo has a 2 year warranty but I wouldn't send it back without being 100% sure that it is the problem.

I checked it with vag-com but no fault codes show up. Now the car seems to be running sweet but i think i'm still going to replace those vacuum lines just to be sure...

Thank you very much for the links!

[Steve Q]

You're welcome, glad I could help and glad the links we're useful :) 

Keep us posted on how you get on :) 

Cheers

Steve 

[Diggy98]

Hello, I didn't have time to order and replace the hoses but noticed a new thing when taking the car for a spin today. When the "power loss" occurs, the accelerator pedal feels more laggish (I press it and for the first 1-2 centimetres nothing happens, I press it deeper and it doesn't accelerate immediately), I think that this might help in diagnosing the problem. What is confusing as hell is the absence of fault codes...

[Steve Q]

Hmm I do wonder if the lag is the turbo then. This is the same symptoms my sister experienced in her mk4 golf. As I say if it is the turbo then blades could have broken off the fan. 

[Diggy98]

Hi, Steve. If the turbo was the problem, then why would it have moments when it runs like a charm? As far as i know, when the turbo goes bad, it goes bad for real (especially broken blades) and can't misteriously come back to working condition...

[Steve Q]

1 hour ago, Diggy98 said:

Hi, Steve. If the turbo was the problem, then why would it have moments when it runs like a charm? As far as i know, when the turbo goes bad, it goes bad for real (especially broken blades) and can't misteriously come back to working condition...

Well I've only compared it to my experience of my sisters golf. And I did see the turbo fan which had blades broken and meant the car didn't run 100% all of the time. But I could be/and probably will.be wrong but I've based it on my.own experience. 

[Diggy98]

I understand...will take a look to the turbo too when i'll check the car next week as it shouldn't take me too much time. Thank you for your help! 👍

Also, a friend that had a similar problem (it think it's more or less the same from what he described) suggested me to check all the vacuum lines including the vacuum tank. Does anyone know where this tank is located? And maybe how much vacuum hose I would need and what the proper diameter is?

 

[Steve Q]

You're welcome :) 

Sorry I can't help anymore though and I'm unsure where the vacuum tank is to be honest.

Cheers

Steve 

[Diggy98]

It's ok Steve, you've already helped me a lot, thanks :)

[Steve Q]

2 hours ago, Diggy98 said:

It's ok Steve, you've already helped me a lot, thanks :)

You're welcome :) glad I could help :) 

[Diggy98]

Had the time to do some checks in the weekend...I took a friend with me and took the car for a spin with the vag com connected in order to check the turbo pressure. It is very good, there are only a few milibars of difference between how it is and how it should be, checked from idle to 4500 rpm. So I guess that the turbo, pipes, vacuum lines and intercoolers are out, since there is no over or underboost. I will replace the fuel filter tomorrow, hope for the best!

[Diggy98]

I replaced the fuel filter and it seems that the problem is gone. Now I wonder if running with that dirty filter may have caused damage to the injectors...should I use some cleaning solutions? Or is it better to leave them as they are?