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Rough idle when cold. Rate Topic: -----

#1 User is offline   Gabs 

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Posted 27 July 2018 - 04:13 PM

Hi all,
My 2014 Touareg was suffering from a quite rough idle/missfire when cold. Well, I should rather say, summer cold mornings...
Anyway the exhaust fumes were quite itchy to the eyes and not until the engine had warmed up it ran smoothly.
Two days ago I had some spare time in the afternoon and decided to bit the bullet. Connected mylaptop and according to VCDS no faults pressent. I checked the intake air mass flow and it turned out that the actual air flow was half as much of the required. As the air filter was brand new I ruled it out as the problem. Had a look at the air mass flow meter and it looked sound too. So I thought that there was a restriction somewhere.
Disconnected the intake air hose at the throttle valve upstream of the EGR intake and with the engine running the butterfly valve, was opening and closing erraticaly. When it was open the engine idled ok, but as soon as it closed it sttutered. I clean some oily residue from the butterfly and its track but it made no difference.
As it was difficult to spot the condition of the swirl flap unit, possibly the following restriction, I operated it via VCDS output tests and I found that it was quite sluguish, therefore I belived that it could be the culprint.
I therefore disassembled the first section of the intake manifold, the one that according to VW literature should be soot free because "deposits on the inside plastic wall can be avoided in all operating modes thanks to the geometric shape" and to my surprise it was very badly covered in soot subsequent to the EGR intake, which was quite sooty too. But to my dismay, the swirl flap unit was covered in as much as 10mm of soot all over the place!!! No wonder that the butterfly valve was sluguish...
Anyway, I disassembled it and removed all the soot and crude from the intake manifold and the swirl flap unit, and as much as I could from the second section of the intake manifold that feeds the cylinder banks. Then assembled all the bits and bobs, and luckily after cranking up the engine it idled smothly at 700rpm.
Now I am a happier Touareg owner. :-)


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#2 User is offline   NoobyT 

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Posted 27 July 2018 - 05:41 PM

Well done.

Good write-up from problem, to thinking it through, to final fix.

I enjoyed it.

Thank you.
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VW Touareg models are as follows:
Generation 1: T1 is model 7LA and the facelift T2 is model 7L6
Generation 2: T3 is model 7P5 and the facelift T4 is model 7P6
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Brilliant site with a lot of information and many photos of all the Cayenne models since launch!

#3 User is offline   xentry 

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Posted 27 July 2018 - 08:22 PM

Great write-up.
Could poor quality diesel have been the start of the problem? Or, too much city driving ?

#4 User is offline   Gabs 

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Posted 28 July 2018 - 04:43 PM

To be honest I have not got a clue.
I know that the previous owner lived in Barcelona but do not know what his driving habits were.
When I had to replace the swirl flap linkages of my 3.0 TDI Phaeton, at about 200.000km (125kM), I found some soot at the intake manifold and the intake runners, but not tho that extend. What it was almost clogged was the feeding port of the EGR system.
I do most of my driving on motorways and use good quality fuel. I guess that both somehow make a difference.


#5 User is offline   Black Grouse 

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Posted 28 July 2018 - 05:13 PM

Since fuel isn't normally present in the intake side of the engine, this soot may be carbonised oil if the turbo seals are defective or from excessive blow-by if the engine is badly worn - neither being a good prospect.
2016 MY Touareg SE 262 - Reef Blue

#6 User is offline   kidcrew_bob 

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Posted 22 August 2020 - 10:00 AM

I have exactly same issue - done air & fuel filters, checked & cleaned MAF sensor (didn't seem dirty) to no avail - as you found, a little light oil inside the first intake aperture next to inlet - but seems I need to go further. Do you have and pics of the disassembly or link to a diagram that could help me - sounds fairly straightforward but don't want to screw something up....

2013 T3 245 "Escape" in silver and charcoal interior, CDC air suspension, parking-heater, 100 litre tank, Dynaudio, panoramic roof, area view, electric towbar, 20" Pikes, 12-way nappa climate seats with dual memory pack, adaptive cruise control, Bi-Xenons, 4-Zone climate, rear sunblinds, black piano insets, keyless go, electric / auto tailgate, heated front screen & steering wheel - 33 mpg lifetime average.

Previous: 2011 T3 "Escape" dark grey /walnut inserts, CDC air suspension, 100 litre tank, Dynaudio, pano roof, 17" Karakums, 12 way vienna, dual memory pack, rear sunbinds NO REAR LEDs ;-) 31 mpg ave
Previous: 2009 Audi A3 1.6 DSG - 50 mpg average
Previous: 2006 Seat Altea 2.0 DSG - one of the most reliable cars I've ever owned! 47 mpg lifetime average.
3 x troublesome and very expesive to run & maintain Range Rovers - best of which was the 1988 3.9 v8 Vogue SE - the diesels couldn't pull the skin off a rice pudding - all <20mpg !!!

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