Hello to everyone!

I'm owning a 2013 Octavia Rs 2.0TDI with the famous CUN engine. Preveously I had oil consmption issues with the car 1l/700km. In September I've rebuilt the engine and successfully reduced the consumption not to zero but I can live with the current state.

Parts I`ve changed:

• Piston rings

• refurbished cylinder (all the parts)

• refurbished turbo

• crankshaft bearings

• con rod bearings

• all the sealings

• etc.

So I changed quite a lot. And done it for myself. Previously I did the same on my old car 2010 Farbia Rs CAV (I loved that car).

My current issue is that ONLY on cold start I have start up issues. Sometimes long cranking (5-7sec, starter motor hase been changed recently) or starts right up but with rought idle. After a few segonds the rought ide is gone and runs perfectly. I took all 4 injectors to a specialist who made measrements on them and they are perfect. I`ve tried to change the fuel brands and nothing changed, also tried with premium fuel (I live in Hungray so I tried Shell and MOL but also tried with fuels from different cuntry). During the assembly of the engie I tested the glow plugs and all four looked to be good. Tested with 12V and all of them were glowing. I have no DTC unfortunately. Air and coolant temperatur sensors are showing mostly the same no big differences between them (below 10 degree Celsius differences). Rail pressure on Ignition On is 1520kPa (15,2bar) should it be higher or lower?

While driving I can`t feel and issues even if I floor it no error or interruption. Second issue or anomaly is when the engine warms up somewhere around 60-70°C starts to smoke blue. This blue smoke is present only until I give him a few hard pushes, no flooring it just accelerating a bit harder. I read that a more dense fuel-air mixture can cause this issue and not only oil getting burned. And as I said after a few acceleretions the smoke is gone totally. Unfortunately the DPF was removed by the previous owner and a correct software modification was also done.

Does anyone know what else should I check or maybe has a solution?

Thanks for the help in advnace!

Have a nice day and happy holiday for all! :)

I have an update on the topic. Unfortunately I found out that there is oil in the piston chamber. I’ve bought a camera and had a look inside the chamber. Also made a measurement on the compression and it is perfect. Could it be from the cylinder head cover? I installed a Febi and not an original one. Any ideas?

On 13/12/2025 at 09:53, Atlesz said:

starts right up but with rought idle

It may be the glowplugs or glowplug circuit/wiring/timer?. My old octy had two bad plugs and would start no problem when weather was mild but when cold would still start but would take more cranking and then sound rough until warmed up after 20secs

If your compression test is good then the oil may be coming from valve stem seals but you mention febi cylinder head cover. if you mean head gasket it may be that the febi one is wrong or the head is warped aand your getting oil in that way.

Alasdair

14 hours ago, Alasdair1 said:

It may be the glowplugs or glowplug circuit/wiring/timer?. My old octy had two bad plugs and would start no problem when weather was mild but when cold would still start but would take more cranking and then sound rough until warmed up after 20secs

If your compression test is good then the oil may be coming from valve stem seals but you mention febi cylinder head cover. if you mean head gasket it may be that the febi one is wrong or the head is warped aand your getting oil in that way.

Alasdair

Glow plugs are working and I found no issues with those. Also a faulty plug should report an error/DTC I think. No, I meant the valve cover is Febi. Sorry for the mislead.

Yes a faulty plug should ping up a code. Years ago had a diesel van that gloplugs were ok but timer/sensor failed so they werent on long enough?

Cant see a rocker cover seal causing oil in piston but if your crank case/engine breather is blocked/failed then maybe to much pressure thats forcing oil in somehow and causing smoke. Cant remember how to check it sorry.

Hope you get to the bottom of it

Happy Xmas