Turbo Underboost problem

[joeyrich69]

Having just replaced the N75 valve, I am still having problems with my cars acceleration. The turbo seems to kick in much later than usual, approximately 3000-3500 rpm. It has gone into 'limp' mode a couple of times recently. The car is a 2010 Octavia VRS TDi FL estate. Mileage is 73k, and I believe it is a KKK turbo.

 

Using 'Measuring Blocks' in VCDS I have logged groups 10 and 11, and this shows Actual Boost lower than the Specified Boost at a lower RPM (up to 3000), but the Actual Boost and Specified Boost appear to be very similar nearer 4000rpm.

 

I have done a visual inspection of the hoses, and there does not appear to be any leaks or split hoses.

 

Does anyone have any similar experiences to this? Any suggestions what to check next would be much appreciated.

 

Below is a copy of the VCDS scan.

Chassis Type: 1Z (1K0)

Scan: 01 03 08 09 15 16 17 19 25 42 44 46 52 55 56 62 72 77

 

VIN: TMBUH21Z4A2106539   Mileage: 117590km-73067miles

 

01-Engine -- Status: Malfunction 0010

03-ABS Brakes -- Status: OK 0000

04-Steering Angle -- Status: OK 0000

08-Auto HVAC -- Status: OK 0000

09-Cent. Elect. -- Status: Malfunction 0010

15-Airbags -- Status: OK 0000

16-Steering wheel -- Status: OK 0000

17-Instruments -- Status: OK 0000

19-CAN Gateway -- Status: OK 0000

25-Immobilizer -- Status: OK 0000

42-Door Elect, Driver -- Status: OK 0000

44-Steering Assist -- Status: OK 0000

46-Central Conv. -- Status: OK 0000

52-Door Elect, Pass. -- Status: OK 0000

55-Headlight Range -- Status: OK 0000

56-Radio -- Status: OK 0000

62-Door, Rear Left -- Status: OK 0000

72-Door, Rear Right -- Status: OK 0000

77-Telephone -- Status: OK 0000

 

-------------------------------------------------------------------------------

Address 01: Engine (CEG)       Labels: 03L-906-022-CBA.clb

   Part No SW: 03L 906 022 RD    HW: 03L 906 022 GA

   Component: R4 2,0L EDC G000SG  5751 

   Revision: 13H03---    Serial number:              

   Coding: 0001072

   Shop #: WSC 73430 790 00000

   VCID: 78F9A7470B1102E157B-802D

 

1 Fault Found:

000665 - Boost Pressure Regulation

               P0299 - 000 - Control Range Not Reached - Intermittent

             Freeze Frame:

                    Fault Status: 00100000

                    Fault Priority: 2

                    Fault Frequency: 1

                    Reset counter: 255

                    Mileage: 117537 km

                    Time Indication: 0

                    Date: 2015.01.10

                    Time: 11:31:01

 

             Freeze Frame:

                    RPM: 2668 /min

                    Speed: 90.0 km/h

                    Load: 79.2 %

                    Absolute Pres.: 2437.8 mbar

                    Absolute Pres.: 1672.8 mbar

                    Lambda: 85.2 %

                    Lambda: 31.6 %

 

Readiness: 0 0 0 0 0

[Excision]

Sounds like you have sticking vanes in the VNT mechanism of the turbo, resulting in the vanes sticking in the 'open' position. To investigate this see if you can access and move the actuator mechanism by hand. It might require a fair bit if physical effort but you are looking for smooth movement, with no obvious points of resistance.

Try YouTubing for a VNT turbo mechanism vid to see how it works and look on here for the Mr Muscle cleaning threads for VNT turbos.

[joeyrich69]

thanks for the reply but I think its a KKK turbo not a VNT turbo. Does the KKK work the same way as a VNT?

[robt100]

KKK = Brand
VNT = type of turbo design Variable vane turbos.

So, your turbo is a VNT turbo

[joeyrich69]

OK Thanks. Could my problem also be due to a sticking/faulty actuator?

[Excision]

Could be the actuator but the more common cause is excess carbon deposits on VNT mechanism.

[radders567]

I've not heard many people complaining of the CR turbo playing up due to carbon deposits, I have however heard of the electronic actuator failing.  This may be your case.  As you have access to VCDS maybe you could test it ?

[joeyrich69]

Definitely worth testing the actuator with VCDS but can you tell me how to do that, Thanks

[sniper29a]

sticky vanes. at about 3500-4000rpm is max. revs of turbo and vanes are open.

 

take turbo out - clean everything.

 

if that doesn't help (as in my case), turbo is dead and you need new one.

 

there is simple test...warm up your car...drive it on flat road on third gear....let revs drop to 1500revs and then floor it...it will slowly accelerate and by 1750revs it gets really kick in (where turbo starts to rev up).

 

Unsure about where your car starts to kick in but you seem to have similar car to mine...1750revs.

 

There is also test in VCDS - you can see all what is moving...if lever for vanes doesn't move then you have sticky vanes or vacuum hoses are ruptured. you can easily try with hand - if you can access turbo, just pull/push the lever for vanes...it must move really smoothly.

[mroberts]

Talking of VNT. i have a 140 TDI PD

 

I have cleaned mine on the car whilst getting rid of the EGR & Cooler.

 

How hard is it getting the exhaust manifold off, and associated pipework (Oil and Air) to clean the turbo properly, as some brigh spark at VAG made the Manifold and Turbo 3 parts ( manifold / bearing and shaft housing, VNT and cold side) instead of a turbo bolted to a manifold.

 

I only ask as im pretty certain the best clean can only be obtained by removing it and not doing it by guess work on the car. i couldnt find anything on how to remove the exhaist manifold and turbo unit on here.

 

I used the innotec cleaning kit for mine.

[sniper29a]

I did it only on Fabia but it might be similar.

 

You have to take almost anything off in the way of turbo - air intake to air box. You need best access behind the engine. You have to take EGR off and pipe work because screws/bolts on exhaust manifold are sometimes tricky.

 

Lots of swearing and patience (swearing in my case :-) - various extension, adapters to get eight screws off. They will be most likely rusted by heat. Always use copper grease afterwards.

 

My friend mechanics always said - best cleaning is petrol and burn the manifold out. There is usually lots of rubbish. Oil sooth, carbon deposits and so on. Sometimes new manifold is best solution.

[joeyrich69]

Just an update in case anyone has the same problem, the actuator has been replaced by Hadwins VW for about £330, and this seems to have solved the problem. Thank you for your input.