Second Issue - Rough Idle

Here’s another problem I’m investigating before my warranty expires (I posted a different problem yesterday).

First some specifics about my mk6 GTI:
- Model Year: 2013
- Second owner
- 17,000 miles (27,500 km)
- Have only used 92 Octane and higher ‘Top Tier’ gas.

The problem:
The engine does not always idle smoothly. For example about half of the times when I’m stopped in traffic, I feel the engine idling rough with ’stumbles’ every few seconds, like a piston failed to fire properly. It typically doesn’t register an rpm change on the tachometer. I simply feel it through the seat. It has done this since I bought the car two years ago.

I figure pre-ignition caused by carbon deposits isn’t the cause because the car is low miles and I have only used ’Top Tier’ gas which is supposed to reduce deposits in the combustion chamber. On the other hand the car burns a fair bit of oil - about 1 quart (litre) per 3,000 miles (5,000 km), so perhaps the oil consumption is causing carbon build up?

Anyhow, my question is:
Do mk6 GTIs normally idle rough?

they're noisy as hell (thanks direct injection) but not necessarily rough... 1 quart every 3k miles is insane... I don't have to add any oil between 5k oil changes... I'd check your PCV (or have your dealer check it since you're under warranty). Between the oil consumption and the rough idle that definitely sounds like PCV issues.

It probably is your PCV! This is the latest revision part number, 06H103495AH


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zef & Carlosfandango:

Would a faulty PCV be the cause of the high oil consumption?
Ya, I agree the consumption rate is insane - not happy about it at all. But VW states that as much as 1 quart per 1200 miles is considered normal. Ridiculous! I figured the engineers were trying to improve fuel economy by designing for wider gaps between the piston rings and the cylinder walls. But then I also other people comment that their car burns very little oil, like yourself.

Apparently there is a TSB out there about the faulty PCV issue. Do you happen to know the reference number for it?

Fyodor Dostoevsky said:

zef & Carlosfandango:

Would a faulty PCV be the cause of the high oil consumption?
Ya, I agree the consumption rate is insane - not happy about it at all. But VW states that as much as 1 quart per 1200 miles is considered normal. Ridiculous! I figured the engineers were trying to improve fuel economy by designing for wider gaps between the piston rings and the cylinder walls. But then I also other people comment that their car burns very little oil, like yourself.

Apparently there is a TSB out there about the faulty PCV issue. Do you happen to know the reference number for it?

Click to expand...

Yes a faulty PCV can explain excessive oil consumption, usually due to it not separating oil and vapour correctly and allowing oil into the intake which is then burnt, It wasn’t always the case but I now have very low oil consumption but I have a new cylinder head and most (if not all) of the engines gaskets and seals are new too so along with also having a new PCV this is probably why I use less now! Oil can be consumed for various reasons such as small amounts getting past valve stem seals or guides and if not excessive will likely go unnoticed apart from higher oil consumption compared to other owners, so due to things like this that’s why we see different cars using different amounts of oil without apparently obvious reasons, turbo cars will always consume oil as that’s just how they work, just on some it’s worse than others for varying mechanical reasons, some have more blow by and some don’t really so it’s all different especially as the cars age.


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Of course it may not be your PCV but with the oil consumption and rough idle it’s a good place to start as it’s easily fitted and is relatively cheap!
https://youtu.be/hQEciqR1ST8

Was pulling so many rough idle threads from the dead really necessary??

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The dealer actually already ran a 'scan' last week on the engine and reported "no codes stored". So I'm still unsure if I really have a problem. But today I also came across a video on YouTube where a guy was burning oil like crazy due to a faulty PCV, but had no engine codes to indicate a problem:

https://www.youtube.com/watch?v=P0c4wM28ex0

Mind you, my car doesn't produce a cloud of smoke like that, but I do have a lot of black soot in the tailpipes.

I also found the TSB for testing the PCV:

https://www.carmd.com/Tsb/Download/96059/V101201

It doesn't specifically say that error codes are needed to indicate a faulty PCV. I plan to do the tests myself on the weekend.

Sorry about all the posts. I didn't realize everyone using this bulletin board would see them. I figured only the OP and people subscribed to the thread would see them.

My drive train warranty expires in less than two weeks so I'm trying to get to the bottom of a few issues before it does.

Fyodor Dostoevsky said:

The dealer actually already ran a 'scan' last week on the engine and reported "no codes stored". So I'm still unsure if I really have a problem. But today I also came across a video on YouTube where a guy was burning oil like crazy due to a faulty PCV, but had no engine codes to indicate a problem:

https://www.youtube.com/watch?v=P0c4wM28ex0

Mind you, my car doesn't produce a cloud of smoke like that, but I do have a lot of black soot in the tailpipes.

I also found the TSB for testing the PCV:

https://www.carmd.com/Tsb/Download/96059/V101201

It doesn't specifically say that error codes are needed to indicate a faulty PCV. I plan to do the tests myself on the weekend.

Sorry about all the posts. I didn't realize everyone using this bulletin board would see them. I figured only the OP and people subscribed to the thread would see them.

My drive train warranty expires in less than two weeks so I'm trying to get to the bottom of a few issues before it does.

Click to expand...

As it can fail in many ways a faulty PCV usually doesn’t throw any codes, just gives symptoms (and these vary widely), it’s sometimes the symptoms that can cause a code but it depends what symptoms you’re getting as to wether that happens! Search the web for how to test for a bad PCV, your issue could be something else so check the PCV first as it’s easy to do.


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Carlosfandango said:

As it can fail in many ways a faulty PCV usually doesn’t throw any codes, just gives symptoms (and these vary widely), it’s sometimes the symptoms that can cause a code but it depends what symptoms you’re getting as to wether that happens! Search the web for how to test for a bad PCV, your issue could be something else so check the PCV first as it’s easy to do.


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Click to expand...

The pcv on these cars sucks ass, that's the real reason :thumbdown:

The existing PCV model number on my car is: 06H103495E (i.e. not the latest model 06H103495AH)

Does anyone know if this model is known to be prone to failure?

Also, I did a few simple tests according to TSB 10-12-01:

+ With engine running, disconnected hose from the manifold and plugged the manifold opening.
Result: No noticeable change to idle quality.

+ With engine running, removed dipstick.
Result: No noticeable change to idle quality.

+ With engine running, removed oil filler cap and placed a piece of stiff paper over the oil filler hole.
Result: Paper was sucked against the hole as it should.

However, there are other tests on the TSB that I couldn't do.

At this point I am also thinking that perhaps the PCV is responsible for the high oil consumption I see (1 quart/3000 miles). I did see a few drops of oil in the end of the hose from the PCV to the manifold when I took it off.

I'm thinking about asking the dealer to test the PCV for proper functionality before the warranty expires. However if they don't find anything wrong with it I would have to pay for the test. Alternatively I am thinking maybe I should just have the PCV replaced with the latest model - in other words roll the dice and see if that fixes the rough idle and/or oil consumption problems.

Carlosfandango said:

Yes a faulty PCV can explain excessive oil consumption, usually due to it not separating oil and vapour correctly and allowing oil into the intake which is then burnt, It wasn’t always the case but I now have very low oil consumption but I have a new cylinder head and most (if not all) of the engines gaskets and seals are new too so along with also having a new PCV this is probably why I use less now! Oil can be consumed for various reasons such as small amounts getting past valve stem seals or guides and if not excessive will likely go unnoticed apart from higher oil consumption compared to other owners, so due to things like this that’s why we see different cars using different amounts of oil without apparently obvious reasons, turbo cars will always consume oil as that’s just how they work, just on some it’s worse than others for varying mechanical reasons, some have more blow by and some don’t really so it’s all different especially as the cars age.

Click to expand...

Carlosfandango:

What was your oil consumption like before you got the new head and PCV?

Do you know the model number of your old PCV, and your new PCV?

My car has always burned a fair bit of oil since I got it at about 17,500 km, about 1 litre per 5000 km, which is high compared to most other MK6 GTI owners, AFAIK. I would think that at this mileage the engine shouldn't have had much wear on it, unless it was damaged by the first owner. But barring engine damage, it leaves the PCV as the most likely cause. Would you agree?

Fyodor Dostoevsky said:

Carlosfandango:



What was your oil consumption like before you got the new head and PCV?



Do you know the model number of your old PCV, and your new PCV?



My car has always burned a fair bit of oil since I got it at about 17,500 km, about 1 litre per 5000 km, which is high compared to most other MK6 GTI owners, AFAIK. I would think that at this mileage the engine shouldn't have had much wear on it, unless it was damaged by the first owner. But barring engine damage, it leaves the PCV as the most likely cause. Would you agree?

Click to expand...

My oil consumption was bad but that was due to the valve stem seals and guides as it would bellow smoke on overrun, I can’t remember the old PCV part number but I do remember it was made in late 2012, the latest revision part number is stated earlier in the thread, as mentioned earlier all turbo cars will use oil, the specific amount VW see as acceptable/normal is stated in your user manual, (in practice though) all cars will be different! Yes, if it were me I’d try a new PCV.


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