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Discussion Starter #1
Trying to diagnose the dreaded hesitation below 2000rpm on my 06 TDI

The car is new to me so I just finished doing all routine maintenance which is as follows:
- New Camshaft
- New black coated followers
- New cam bearings/bolts
- Adjusted PD injectors with new cam
- New timing belt/waterpump/tensioner
- New airfilter & fuel filter
- Replaced engine oil/filter

The car has no check engine lights. In fact I just drove the car 3000 miles from Niagara Falls, NY all the way to Pheonix, AZ with no check engine lights.

I had my friend with VCDS plug into the car and ran the VNT test and we put a zip tie on the actuator to put us at around a 200mbar difference. He also checked torsion value and it was in spec.

Off the light in first gear the car will stumble and let out a puff of black smoke and then clear and be fine. Whenever the car stumbles under 2000rpm it will produce one puff of black smoke and then clear out.

The more I restrict the VNT actuator rod with the zip tie the more low end power I seem to lose.

Without throwing a bunch of money at the car can you guys think of anything this may be?

Thanks in advance

John
 

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This definitely sounds like the VNT actuator but it should get better with the zip tie fix. Especially since you say it lets out a puff of black smoke and then it's clear and fine. It sounds like perhaps you zip tied it past the optimum point? The zip tie won't fix it if the vanes inside are sticking. Can you move the actuator back and forth with a vac pump and feel if it's catching at all? Check out the VNT repalcement DIY for mk5 cars for some background on the issue.
 

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The vacuum will be less at higher elevations but the system makes more vac than needed to run the systems. These all sound like the turbo is not working because it's closed, then poof, it opens up which causes the puff of smoke and power.

Perhaps the thinner air is causing the ECU to change the opening curve of the vanes which fixes the issue?
 

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Discussion Starter #4
Make your own thread. Your elevation issue with your car is irrelevant to the issue with my car.

Its at high altitude's thin air, say 8,200', that our TDI experiences the 2000 rpm puff of smoke and or the mild performance delay at 1,800 rpm.
The TDI is here in Georgia, (elevation 1,100") and not showing any symptoms. Air density percentage has gotta figure in somehow.
 

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Our MY06 Jetta TDI is similarly positioned as the OP ..... hesitation and smoke puff around 1,800 to 2000 rpm. This condition has been present for the past 10,000 miles.
Original owner car, presently at 150k miles. Recent cam & components, TB service, all filters and new EGR (cooler -edit); all less than 1,000 miles ago.

The VCDS test was inconclusive. Maybe something is being missed with the VCDS? I've owned and used the VCDS for 8 years. That being said, I'll try the software program again. Sticky VNT vanes? Intermittently sticky at that??
 

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IDK, but could it be a sticky (and usually leaky) EGR cooler valve? Not the EGR/ASV on top of the engine, but the EGR cooler valve on the lower back of the engine.
 

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Discussion Starter #7
IDK, but could it be a sticky (and usually leaky) EGR cooler valve? Not the EGR/ASV on top of the engine, but the EGR cooler valve on the lower back of the engine.
I've heard that a leaking EGR cooler will create a hissing noise similar to a boost leak which I don't have... Any validity to this?
 

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A big ole "YES" to failing ERG coolers exhibiting hissing noises. The OE production EGR cooler on our TDI lasted 85,000 miles before exhibiting a loud "hissing" noise symptom. That noisy EGR cooler was replaced with OEM new. Fast forward to last week or 149,000 miles, and the 2nd ERG cooler was replaced; a strong exhaust leak/odor prompted its replacement, however there was no noise.

My kids say "Tape a GoPro to the underside of the car and video the ERG cooler operation"
..... Kids ! Where do they come up with these ideas. (brilliant)
 

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I have a 2006 jetta TDI BRM with the DSG auto, I am having this same problem. Just bought the car. When starting from a compete stop the car will stumble, start sounding like an old 12 valve cummins for a second or 2, let out a puff of smoke and accelerate very poorly until 1800 ish rpm. It actually accelerates very poorly until 1800 rpm in all gears. After that point it is fine.

I will be doing a vacuum test on the actuator tonight to see if it is an actuator problem.. my first thoughts were sticking vanes in the turbo.. someone point me in a direction!
 

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Discussion Starter #11
Ok so I had one of recommended TDI mechanics hook up with VAGCOM to my car.

He said all sensors and parameters check out as normal and no stored codes. However he said the ASV valve is sticking which is causing the loss of power choking the engine and then opening. You can hear a large back pressure under the hood and then a "whoosh" as it opens and the power kicks in.

When I cycle the key to on and off with the 90 degree elbow off I can see the asv working as normal though going from fully open to fully closed. I also just took it off and fully cleaned it (wasn't very gummed up) I also inspected the gears and they are like new. Put the car all back together and same issue.

I really don't want to pay $350 for a new asv if it doesn't appear to be broken? What would cause it to get "stuck" ? It operated smoothly by hand with no binding.
 

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thanks, I will look into a way to test this... possibly I can swap the anti shudder valve from my 04 BEW to the 06 BRM... my valve also seems to operate normally and move manually with no problems..
 

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I have a 2006 jetta TDI BRM with the DSG auto, I am having this same problem. Just bought the car. When starting from a compete stop the car will stumble, start sounding like an old 12 valve cummins for a second or 2, let out a puff of smoke and accelerate very poorly until 1800 ish rpm. It actually accelerates very poorly until 1800 rpm in all gears. After that point it is fine.

I will be doing a vacuum test on the actuator tonight to see if it is an actuator problem.. my first thoughts were sticking vanes in the turbo.. someone point me in a direction!
Do you remember what the issue was with your car I am having the same issues now.
 
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