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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKV-A5 Golf/Jettas

VW MKV-A5 Golf/Jettas Discussions area for A5/MkV Jetta/Golf (2005/2006 PD and 2009 CR).

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Old November 16th, 2014, 20:53   #1
OMALLEY_808
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Default BRM Low boost below 1800rpm issue

- 06 Jetta TDI.
- No stored DTCs
- Torsion at 0.5
- New timing belt water pump/cam/followers
- no black smoke or and strange behavior
- Had hesitation and then boost spike at 1800rpm before
- limited VNT to 160mbar difference and have no spike now
- Boost spec vs actual is low until around 1800rpm and then matches again.

VCDS logging confirms low boost. Until 1800+ rpm. VNT actuator holds vacuum and starts moving around -3 and hits the stop at -17


Last edited by OMALLEY_808; November 16th, 2014 at 20:57.
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Old November 17th, 2014, 10:56   #2
jjblbi
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I experienced a similar condition about two years ago with my PD motor. Head had been off car for about 3 months for new cam, followers and head work. Apparently the injectors may become damaged if not kept "wet". I tried many, many fixes and adjustments without success. Eventually installed new used injectors (~$500) and car is back running strong. I am one of 3-4 owners that had this issue after an extended head-off. This may not be your solution but if you had it apart for a while save yourself a lot of grief and try injectors. If that is not the solution you can always resell them. Good luck, John
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Old November 17th, 2014, 11:01   #3
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Yep, sounds like the normal worn out VNT ring in the ol' BW turbo. Very common on the BRMs.
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Old November 18th, 2014, 17:02   #4
OMALLEY_808
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Could one injector cause this issue or is it definitely the vnt ring? Injector #4 on my car has a deviation of about +0.75 from the rest...

Car idles smooth and runs fine otherwise though...

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Yep, sounds like the normal worn out VNT ring in the ol' BW turbo. Very common on the BRMs.
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Old May 19th, 2016, 08:59   #5
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Anyone have an answer if an injector has a deviation of about +0.75 from the rest should be replaced???
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Old May 19th, 2016, 12:04   #6
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By either the zip-tie band aide, or actual stop screw adjustment you got Basic Settings deviation at 160 mbar, then I doubt the worn VNT control ring is the issue here. The fact that you had to correct it means the ring is worn and boost control will be sloppier, but it shouldn't cause a lag.

I recommend another Group 11 log but at WOT in 3rd gear from ~1500 RPM to redline. With this log you can graph actual vs. corrected in a spreadsheet program. If you post that it will be easier to judge if it is laggier than usual or not. With the part throttle log you posted you are not requesting the fueling potential in that region of the log, more fuel (WOT) will provide more exhaust energy to get the turbo spinning faster.

As a side benefit to the above log, you can check N75 duty cycle at 4000 RPM to verify the rod length is correct too. It should be around 25-30%.

Actual NEVER exactly follows requested on spool-up, even in a new car. The ECU requests stronger boost response in that region to spool the turbo within it's mechanical, dynamic limits so you will always see actual lower until the turbo can get up to speed. In other words, you may not actually have an issue.
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Old June 6th, 2016, 21:45   #7
fwthompson
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You can check the vnt actuator very easily with a vac pump and guage like a mity vac. It should hold and begain to extend thru the pumping cycle. But holding pressure is the important part. Theres a good write up on adjusting these if you google it. Idparts sells replacments if yours fails the check. Goodluck.
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Old June 7th, 2016, 19:27   #8
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Subscribed to see how this turns out. I am still seeking answers for a similar issue with my '06 BRM..........Please post up your findings. thxs
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Old June 9th, 2016, 17:28   #9
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I have a mityvac already. Actuator is fine. Changed the fuel filter with the oil change last week and definitely restored some lost power but it still a dog between 1000 and 1500 rpm in anything other than 1st gear.

I'm still leaning towards that faulty injector. I have a spare set but it looks like a pain in the ass to change...

Fuel mileage is good and car pulls pretty hard for what it is once that malone stage 2 power kicks in.
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Old June 10th, 2016, 06:28   #10
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Is this car a DSG?
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Old June 10th, 2016, 13:55   #11
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5spd Transmission
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Old June 10th, 2016, 15:12   #12
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Dont know if youve read the MKV specific thread but alota people reporting this issue. Normally fixed by ziptie mod but even guys with new turbos having the same issue.
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Old June 10th, 2016, 16:32   #13
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Quote:
Originally Posted by GreenLantern_TDI View Post
Dont know if youve read the MKV specific thread but alota people reporting this issue. Normally fixed by ziptie mod but even guys with new turbos having the same issue.
Yeah already played with that. Using a zip tie is a pretty sloppy way of doing it though as it can sometimes jump onto the side of the adjustment nut or the actuator arm, it can also jump around on the VNT nipple or land on the rubber vacuum hose. I used stainless steel mechanic safety wire tied nicely at both ends to prevent jumping around and tried limiting it. Same sort of results.

I dug up a thread with someone who went through all the same checks I have and had one faulty injector and when he changed it, it solved the issue.

Here is the theory. One injector is out of wack (leaking/excess fuel) Computer picks up on this and cuts fuel to the other 3 injectors, as seen by the negative duty on them. This results in underfueling down low, which underfueling will not spool the turbo or accelerate as normal.
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Last edited by OMALLEY_808; June 10th, 2016 at 16:34.
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Old June 11th, 2016, 05:38   #14
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When i get a chance ill run a VCDS and check to see if ive got a - value as well.
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Old June 16th, 2016, 12:15   #15
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So im seeing negative injector diviation numbers too.
-.15 -.49 +.12 +.45
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