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Discussion Starter #1
Hello, I have a 2006 Jetta TDI (BRM) which has acquired a shudder. The shudder occurs immediately upon acceleration or when trying to maintain speed. When accelerating from a stop the car will accelerate and then fall on its face for a second and proceed normally. Usually when the shudder occurs during acceleration it is followed by a puff of black smoke. When the shudder occurs while trying to maintain speed it is typically below 2000 RPM. Typically it will also occur after the car is up to operating temperature and more often when the weather is more extreme (i.e. high temperature). The car has had the timing belt replaced at 100k and now has 104k on it. The car has a Kerma ECU tune but the shudder occurs in the stock and modified settings. The torsion value post timing belt change has been confirmed to be within the recommended range (with VSDS). Does anyone have any ideas? Any suggestions are appreciated, thanks!
 

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Discussion Starter #5
The injector deviation is never more than .49mg/stroke, I understand it needs to be within .6mg/stroke so I'm guessing this isn't the problem. I also tried the boost leak and the system definitely has no leaks when hot or cold. The only thing that seems to help is unplugging the MAF, but this also disables the EGR I understand. Disabling just the EGR throttle by itself does nothing to help the shuddering or the smoking. When the MAF is unplugged there is no smoking and no shuddering. Is there any reason to believe it isn't the MAF?
 

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I don't know why the MAF would cause that kind of shuddering but it's possible. You mentioned VCDS, I would have a helper do a data log while you drive and try to replicate the condition before spending money on a part.
 

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Turbo Overboost?

This could be an overboost issue. I had this quite bad and left a huge black cloud at least once per ride. After studdering for a second, the car would suddenly engage and take off like a shot leaving the black cloud. It also had studders while driving at low rpm.

If this sounds familiar, take a log of module 011. compare 'boost specified' to 'boost actual'. Actual will normally overshoot specified a bit when taking off but it shouldn't be above it while cruising. Before fixing my overboost, there were times where I was highway driving and the specified boost was 1000mbar but the actual was 1500. It's too late but tomorrow I will try to figure out how to post some of my graphs

Another quick but not as good way to tell if you have overboost is to run the basic settings test for 011. This will bring the rpms to 1400 and cycle the turbo on and off. The difference in actual boost between on and off should be 80-100mbar. Mine was 300 (980 off vs 1280 on).

There is recent info on tdiclub on how to adjust the turbo adjustment screw to solve this under a post '...black smoke under 2000 rpm'
 
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