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I recently bought a 2011 V6 Touareg I've had it about a month. I took it in to the shop and had the plugs, coils, oil change, filters etc done. The car runs rough for about 30 seconds on a cold start and then it evens out. My mechanic hooked up the diagnostic to it and couldn't find the fault. He said as it progresses it will trigger the code and he can then correct it. Any idea what it might be? The Touareg is in excellent condition visually and mechanically, I'm just stumped by what this might be.

I will say, I love this car. I was originally looking for a Cayenne but when this Touareg popped up at $10-12K less than a Cayenne I pulled the trigger. Can't say I'd ever buy a Cayenne as this car IMO is just as good (Cayenne owners disagree) but, I've extensively driven both.
 

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My first guess would be a fuel issue.... have him look over the fuel supply closely.... it almost sounds like the fuel pressure is lost due to a small leak or something...... how long have you driven it since? Does it act the same way if you shut it down and start it 1hr later, or only after a prolonged sitting?
 

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My first guess would be a fuel issue.... have him look over the fuel supply closely.... it almost sounds like the fuel pressure is lost due to a small leak or something...... how long have you driven it since? Does it act the same way if you shut it down and start it 1hr later, or only after a prolonged sitting?
Only after sitting over night. It's been doing this since I bought it. I didn't notice at the dealer because they had previously started it and moved it around before I arrived.

I looked more on the forum and it appears this isn't an isolated issue. Seems people are tight lipped about this issue but, a "software remapping on startup" is what I've read... I'm skeptical as to that answer.
 

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This might not be 100%, since you list a 2011, but this is one thing to check.

It might be 100% for your T3. I know it works for T1 and T2.

 

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My '11 does the same thing. It's got new OEM plugs/coils/filter and recent oil change. Seems to be more rough/noisier on cold starts in warmer weather. Smoother/quieter cold starts in colder weather < 35° F.

Some people have said this is due to the engine working to build up the oil pressure. Not sure if this is the case or not.
I was leaning to the possibility of carbon build up on the back of the intake valves being the culprit.


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I was leaning to the possibility of carbon build up on the back of the intake valves being the culprit.


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..... because you're running Summer carbon buildup instead of All Season carbon buildup? Or 30sec carbon since it goes away after?

Also, if people say it's due to oil pressure building up...... is the oil more viscous in warm weather or cold weather?

You guys should pull your plugs after the vehicles sit overnight to see if your cylinders smell like gas.... I'm suspecting leaky injectors.
What sort of milage are you at?
 

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..... because you're running Summer carbon buildup instead of All Season carbon buildup? Or 30sec carbon since it goes away after?

Also, if people say it's due to oil pressure building up...... is the oil more viscous in warm weather or cold weather?

You guys should pull your plugs after the vehicles sit overnight to see if your cylinders smell like gas.... I'm suspecting leaky injectors.
What sort of milage are you at?

At least you gave another possible scenario to the problem rather than just being a Richard Cranium about other peoples theories.
Presently I have ~82K miles but the Treg has been doing it since I purchased it used with ~72K miles on the clock.


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Theoretically, a leaky injector would potentially cause a rich condition after sitting which could "clear up" as you guys are describing once the engine started and a few hundred cylinder explosions too place.... Smell your oil... I should stink like gas if this is severe enough.
 

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This is a normal 3.6 VR6 FSI characteristic caused by the Homogeneous Split Catalytic Converter Heating Method-And no I didn't just make that up. This is described on page 37 of the 3.2 and 3.6 VR6 Self Study as:

"This system has the task of quickly heating the
catalytic converters to operating temperature for cold
starts.
Fuel is injected twice in a combustion stroke.
The first injection occurs in the intake stroke. This
creates an even distribution of the fuel/air mixture.
In the second injection, a small additional amount
of fuel is injected just before ignition TDC.
The late injection increases the exhaust gas
temperature. The hot exhaust gas heats up the
catalytic converter so that it reaches its operating
temperature faster."

During this cycle the engine will run a bit odd...which is normal. The plus side to all this is that there is no secondary injection air pump.

The most common way of describing this is that the motor can sometimes sound like it has an aggressive cam and can even erect forward or backward creep by being a bit rough. Note that there is also a different (and much deeper exhaust note (if you put your ear down there).
 

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This is a normal 3.6 VR6 FSI characteristic caused by the Homogeneous Split Catalytic Converter Heating Method-And no I didn't just make that up. This is described on page 37 of the 3.2 and 3.6 VR6 Self Study as:

"This system has the task of quickly heating the
catalytic converters to operating temperature for cold
starts.
Fuel is injected twice in a combustion stroke.
The first injection occurs in the intake stroke. This
creates an even distribution of the fuel/air mixture.
In the second injection, a small additional amount
of fuel is injected just before ignition TDC.
The late injection increases the exhaust gas
temperature. The hot exhaust gas heats up the
catalytic converter so that it reaches its operating
temperature faster."

During this cycle the engine will run a bit odd...which is normal. The plus side to all this is that there is no secondary injection air pump.

The most common way of describing this is that the motor can sometimes sound like it has an aggressive cam and can even erect forward or backward creep by being a bit rough. Note that there is also a different (and much deeper exhaust note (if you put your ear down there).
I love actual knowledge\advice! It's hard to sift through all the random crap most users throw out at people's problems without actually using anything to back it up, or without using any logic. I told you guys it sounded like a fuel condition.... I just wasn't familiar enough with that particular motor\system to identify that it's normal. I just learned something... it's a good day.
 

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I love actual knowledge\advice! It's hard to sift through all the random crap most users throw out at people's problems without actually using anything to back it up, or without using any logic.
Exactly...hopefully nobody wasted their time pulling out all of their spark plugs looking for a leaky injector.




Now that Spiegelglatt posted that I recall reading about that also, just forgot.


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Exactly...hopefully nobody wasted their time pulling out all of their spark plugs looking for a leaky injector.
.
You're funnier than usual today.....
I guess cleaning intake flaps would've been much quicker huh?

Thank God I don't have any spark plugs.... I'd probably waste 15min otherwise pulling 6 plugs unnecessarily trying to troubleshoot a condition :wink2:
 

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LOL...just havin' some fun with it.


I think it would take me more than 15mins. just to finish my coffee and a cig. before I started the job.


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Yes, Homogeneous Split Catalytic Converter Heating Method can contribute to rough at cold star with the VAG 3.6L FSI engine.

But, that cold start rough running condition is less pronounced at higher ambient temps than during cold ambient temps.

More likely, a failing/failed PCV is the true culprit of rough cold start regardless of ambient temps.

VAG 3.6L FSI engines sludge easily, especially if oil drain & oil filter replacement intervals are not strictly followed. Oil sludge attacks the PCV rubber membrane and eventually hardens the rubber causing the rubber PCV valve membrane to eventually tear and leak/fail.

When the PCV completely fails the MIL fires and typically throws DTCs P0171 (System Too Lean Bank 1), P0174 (System Too Lean Bank 2) and possibly P0507 (Idle Control System RPM Higher Than Expected).

Unfortunately, on the VAG 3.6L FSI engine the PCV is integral to the cam cover. So, typical VW garage - Indy or Stealer - PCV replacement requires replacing the complete cam cover with new OE cam cover part at significant total repair cost - i.e. US$700 - US$900+.

Until now...

The PCV rubber sealing membrane that is integral to the VAG 3.6L FSI engine cam cover CAN BE REPLACED independently w/o replacing the complete cam cover with a new OE cam cover part. Search eBay for this part -

VW Audi 3.6 & 3.2 Engine Valve Cover PCV Valve & Seal Diaphragm membrane

The improved replacement PCV rubber sealing membrane part is ≈$30.00. About 3-4 hours labor to R&R the intake manifold, the cam cover and replace the failed PCV membrane inside the cam cover and viola! you're back on the road with smooth-running cold starts.

I used this replacement PCV rubber sealing membrane part myself to solve the THIRD failed PCV in ≈140k miles on my Treg. Yes, oil drain and oil filter replacement intervals always followed using correct spec oil.

Basically, the OE PCV rubber sealing membrane is proven to be a deficient part prone to repeat failure. Nice little Touareg 3.6L V6 'quirk' for VW garages.

Cha-ching!!

Thus, can suggest grabbing more than one replacement PCV rubber sealing membranes for future use.


Cheers!

Moto
 

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Yes, Homogeneous Split Catalytic Converter Heating Method can contribute to rough at cold star with the VAG 3.6L FSI engine.

But, that cold start rough running condition is less pronounced at higher ambient temps than during cold ambient temps.

More likely, a failing/failed PCV is the true culprit of rough cold start regardless of ambient temps.

VAG 3.6L FSI engines sludge easily, especially if oil drain & oil filter replacement intervals are not strictly followed. Oil sludge attacks the PCV rubber membrane and eventually hardens the rubber causing the rubber PCV valve membrane to eventually tear and leak/fail.

When the PCV completely fails the MIL fires and typically throws DTCs P0171 (System Too Lean Bank 1), P0174 (System Too Lean Bank 2) and possibly P0507 (Idle Control System RPM Higher Than Expected).

Unfortunately, on the VAG 3.6L FSI engine the PCV is integral to the cam cover. So, typical VW garage - Indy or Stealer - PCV replacement requires replacing the complete cam cover with new OE cam cover part at significant total repair cost - i.e. US$700 - US$900+.

Until now...

The PCV rubber sealing membrane that is integral to the VAG 3.6L FSI engine cam cover CAN BE REPLACED independently w/o replacing the complete cam cover with a new OE cam cover part. Search eBay for this part -

VW Audi 3.6 & 3.2 Engine Valve Cover PCV Valve & Seal Diaphragm membrane

The improved replacement PCV rubber sealing membrane part is ≈$30.00. About 3-4 hours labor to R&R the intake manifold, the cam cover and replace the failed PCV membrane inside the cam cover and viola! you're back on the road with smooth-running cold starts.

I used this replacement PCV rubber sealing membrane part myself to solve the THIRD failed PCV in ≈140k miles on my Treg. Yes, oil drain and oil filter replacement intervals always followed using correct spec oil.

Basically, the OE PCV rubber sealing membrane is proven to be a deficient part prone to repeat failure. Nice little Touareg 3.6L V6 'quirk' for VW garages.

Cha-ching!!

Thus, can suggest grabbing more than one replacement PCV rubber sealing membranes for future use.


Thanks for the info, just ordered one
 

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Just ran across a TSB for the rough idle on cold start. TSB # V011331. Apparently there is a software update for the ECM. Any thoughts? I'll attach the TSB. My Treg is running one of the old software versions #8643.
 

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