I recently got hold of an extremely cheap 2014 Octavia Combi with 220000 km on the clock.
Seemed alright when I triued it out BUT!
First sign of trouble was realising that it was using 1liter of oil every 1000 kms. The diesel consuption is also very high at ca. 10Liters per 100kms. No sign of a leak or smoke at the exhaust!
Managed about 2000kms and the car went into limp home mode, the orange corkscrew light came on with messages like ACC and Front Assist not available. My diagnostic found  a P0299 error - new pressure regulator fitted - no improvement at all.
Now apart from the high oil and diesel consumption, the limp home mode I have noticed a number of other strange happenings.

There is huge pressure blowing back when I remove the oil cap or indeed the dipstick.
And the motor fan always runs on when I stop the car, even if I only drove 10kms. The tickover is sometimes 750 and more often 1000 RPM.
I had the car at the local VW dealer and they replaced this pressure regulator valve but are baffled as to what the causes now of my problöems are. All they can suggest is to fit a new DPF and see if that helps. My diagnostic is now telling me that the turbo is not delivering enough boost.
Can anybody help me!

Positive crankcase pressure is normal but yours wheezing like a 40 a day smoker will no doubt be quite extreme.

 

High tickover, high fuel consumption and fan running after shutdown are all indications that it is permanently trying to regenerate the DPF, have someone do a VCDS scan to find the soot and oil ash loads plus differential pressure.

Sorry to tell you but these CUPA engines are known to have high oil consumption when long oil change intervals are used, and not only.. The DPF is most likely full and tries to regenerate all the time because of the high fuel and oil consumption.

 

There are plenty of forum threads here like this one

 

I had a fair few issues recently on the same engine. 2015 Octavia 3 vRS 2.0 TDI (CUPA). 

 

Symptoms included

• Loss of power
• P0299 Turbo underboost DTC
• Fan running for extended periods of time
• Poor fuel economy
• Burning through oil like nobody's business (from full to empty in 600 miles average). 

I spoke to a fair few VW "Specialists" who all said that given the cars high milage 197,000 that this would be a turbo failure and quoted me +£800 for a replacement. 

 

Checked the DPF and it appeared it was fully blocked with a back pressure of approx 5 psi.

 

Cleaned out the DPF and the car works a treat. 

The high oil consumption is definitely not a myth. Mine got from 1L / 2000km to 1L/600km. Had the piston rings changed this February and it got waaaay better. Still uses some, but it might be due to the fact they're not yet seated. Added like 500ml / 4500km.

The consumption and fans running, is due to DPF regen being always on. If you drive more than 90 min without shutting down the engine, the DPF light will come on your dash.

The limp mode can also be caused by the clogged DPS. This also used to happen to me, under heavy acceleration.

 

If you are lucky enough to have a 'good' DPF part number, you can only replace the filter part, and not the whole assembly, why is way cheaper (https://www.autodoc24.ro/as/18989355 something like this, it is basically clamped and can be removed. Mine is welded in and it cannot be changed like this).

Well, I have solved many of the problems and thereby perhaps gained a new one or two!
Firstly, as several of the above folk suggested the DPF does indeed seem to be the root of much evil.

However fixing it is definately not easy. I obtained a new DPF, got the car up on the lift only to discover that the DPF and the Cat are welded together. It appears I mush replace both together.
Next problem, how to replace the Cat and DPF.
It would appear to be eithe an engine out job or a drop the entire front suspension. There does not seem to be anything like enough space to remove these items otherwise. If anybody has a suggestion I would be most gratefull.

An alternative fix which I have implemented is rather controversial!
I remover the exhaust pipe from the DPF and using a 10mm drill and a hammer and chisel I have removed much of the porcelain element in the DPF. Finally some exahaust gasses can pass through
Much fixed. Now the motor is using considerably less than half the diesel as before, the running on of the ventilator is stopped, no more limp home mode and masses of power when I accelerate. BUT......................

Certain errors are now showing up eg. P0401 and P2002.
Obviously this is only a very temporary fix but does allow me to see clearly that the investition in a new DPF is necessary this and will be made in the next few weeks. Or sooner if somebodey tell me how to do this without removing the engine!

It is not an engine out job. You need to move the steering rack out of the way.

If the filter canister can be removed (it is clamped and not welded) you can find a replacement part for around 600euros. Otherwise it's around 2k.

 

This would be a clamped DPF canister.

Edited 3 August, 20232 yr by BogdanB

Thanks for this Bogda. Mine is sadly quite definately welded together. Thanks for the tip about the steering rack.

The good news is that I can, here in Germany, get a new DPF for 390€ and the combined DPF and CAT for 730€.