Shaking harshly at 90° C. No error shown in the dashboard.

Skoda Octavia Mk 3 2.0 TDI 150, 2016, Mileage: 270 K km.

My Skoda has been making some strange shakings since February. Around the time the engine heat hits 90 degrees, which is normal running temperature, the car shakes harshly, sometimes smoothly, sometimes just once, sometimes 2 or 3, or more, with irregular laps in the following 1 or 2 minutes. During these shakes, the rpm responds and it goes up and down, as I try to speed up to compensate it. After this, the car runs smoothly despite its mileage. I can come up to 140km/h but usually stay around 120-125 in the highway. No problem at all. I have never received any error message on the dashboard. The problem occurs in every ride, but not if the engine heat is already at 90 C.

During the last 4 months I have tried a lot, and changed a few parts. Lastly water pump, because “sporadic” water pump problems was registered (no dashboard error message shown at any time.) During the last 3 months: Lambda probe (lambda sensor) is changed. Fuel injectors are changed. Pressure regulator is changed. Electric system has been checked (with no errors). I did a diesel system cleaning treatment in March, with Syprin and changed the fuel filter there after.

Since the problem occurs when the heat achieves a certain level, (never below 80, anyway) I expect this to be a clue.

I will truly appreciate if you share your experiences and/or recommendations, would you have any of this kind. Thank you in advance.

NOTE 1. Another type of shaking (sometime after it is warmed up) is happening when I hold at the traffic light, both the clutch and brake pedals are down. In this situation the shakes are quite different but continues until I release the brake pedal little, may be a few centimeters or three. I do not know if these shakes could be related to the no. 1 problem, described above – because the second type of shakes started recently.

NOTE 2. 2 days before the problems occurred for the first time, I drew into a soft snow drive, appx. 30-40 cm. deep, and could drive back after half an hour’s struggle. The car was parked outside in the snow storm during the following 2½ day. I do not know if this has anything to do with the problem, but this is part of the story.