Rough idle & engine konking out - MY16 Polo GTI 1.8 DSG

[Tobes_WIR35]

My wife's car has had a bit of a rough idle for the last little while (I rarely drive it or go in it), say a few months. It wasn't bad, but enough that I noticed it and said to her to mention it to the dealer at her next service. She only does about 5000kms a year, so her services are 12 months apart, next one not due until November. Car only has about 12,000kms on it, it's pretty much brand new, never been flogged. Probably never even seen redline.

Anyway, about a week ago, she phoned me as she was driving in heavy traffic. the auto-stop/start would turn off the engine, then when she was about to go it would start, but then konk out straight away and start again. I told her to turn off the auto start/stop for the time being.

Yesterday she was driving home from work and it did it again a few times, then the CEL came on. She was nearby to our local VW dealer so I told her to just drive it straight there, which she did.

It has also been doing a loud-ish induction whine which it didn't do previously. This may be totally unrelated, but I did mention it to the dealer at the last service and they looked at it and told me it was normal.

Anyway, just wondering what you guys think this issue might be? I'm wondering if it is a carbon build up due to only doing short stints of 5km to work and back?

[Tobes_WIR35]

Ok, update. VW have said the turbocharger has failed (from overheating), and there is also a small leak in the sump - apparently two separate issues. Will be getting a new turbocharger and a new sump. All covered under warranty, so not too concerned, however it does lead me to wonder what caused the failures, unless it's just a simple case of isolated manufacturing defects. I'm wondering if there is sludge in the oil that has caused a blockage in the turbo oil line and hence the turbocharger overheating?

I asked them if the oil level got low from the leak, but they said no it was only a tiny drip.

[GTI_DownUnder]

Turbo overheating failure?

Ok, update. VW have said the turbocharger has failed (from overheating) <snip>.

Your symptoms sound different to the issue I experienced with my GTI but I would note that VW had a defective batch of turbochargers fitted to (Late MY16 early MY17?) MY16 - MY17 GTI Polo's.
I would ask to see the Turbo body that they remove (or have removed). If the impeller is difficult to turn it could be due to overheating/ restricted oil flow as VW have stated.
If the impeller turns freely but has some very small slop/ play when you try pushing the nose of the impeller shaft up or down it is a defective bearing issue. The amount of slop/ play will be very small (1 mm orless?) at the end of the impeller shaft but it is enough for the impeller fins to come into contact with the turbo housing. The batch of defective turbo’s used by VW had poor/ loose tolerance bearings that caused the above issue.
My early MY17 GTI turbo was replaced at about 10K due to dud bearings and I got to check the removed turbo.
In my (non expert) opinion, oil sludge is unlikely to be a contributor to your issue, if changed every 12 months, even with short trips.
Would need to run a car for several years before a sludging issue was likely to arise even with older less refined oils.

[Tobes_WIR35]

All fixed now. They replaced the turbo, changed the oil and replaced the sump. Did a compression test. It's now idling smoother than ever, and feels significantly more powerful under full throttle. All covered under warranty.