Thank you to the collective – to the service manager; to the mechanics, who repaired my car; to the manager, who fought for the warranty rights. This time, I can say only welcoming words – I left the car and keys, and after 2 days – I received the vehicle and keys. Exactly so simple.
Returning to the technical things.
Symptoms of the problem:
a. jerky acceleration (and maintenance of torque). Especially pronounced – for partially warmed engine;
b. robust reaction of the engine to the changes of required torque;
c. uneven idle.
No error messages in the DME error message memory. The “old” VANOS test passed successfully. The new VANOS test (available in ISTA from the beginning of 2022) fails.
Differences in the tests.
The old VANOS test (test sequence is repeated several times):
a. when closing the VANOS valve, the camshaft position and its jittering are checked; compared to the reference position;
b. the camshaft is moved to the actual position; the exact position and its jittering are checked.
The new VANOS test (test sequence repeated several times):
a. the VANOS valve is closed, camshaft position and its jittering are checked; compared to the reference position;
b. the camshaft is moved to the actual position; the actual position and its jittering are checked;
c. additionally: the camshaft position is changed relatively by 40 degrees (against the reference).
Allowed jittering/position displacement for both tests: +/- 5 degrees.
Exactly this moving of the VANOS hub for 40 degrees turned out critical and formally confirmed the problem/served as evidence for the dealer and the insurance company.
Expert mode, VANOS, after repair:
In the image: required and maintained positions of both camshafts (in absolute units and relatively against the reference positions); PWM data of the valves. All curves are perfectly stable!
In the image – zoomed-in PWM values of the valves.
To maintain stable positions of the camshafts, PWM of the valves (Axys 3) are changing only for +/-1 .. 2 %. An excellent result!
Here, how the assigned and maintained positions of the exhaust camshaft (the more problematic) positions before and after repair look.
Pay attention to the scale of the Y axis: before repair, the jittering of the exhaust camshaft (black curve) was +/-10 degrees (Axys 2); after repair, it is reduced to +/-1 degrees, which means 10 times! In addition, as we see, DME is not “twitching” the assigned position of the camshaft!
I did not blur the VIN number deliberately – it will prove that precisely the same car and the same menu are displayed.
Idle after repair:
Performance of all cylinders(Axys 2) – perfectly even; mechanical efficiency – identical, its differences are not more than +/- 1 .. 2 . Perfect!
Performance of Valvetronic after repair:
In blue color – position of the rotor of the management motor. The position is stable; it changes for +/-5 ..10 degrees (Axys 3) during 20 seconds.
Performance of the engine after repair:
a. jerky acceleration disappeared completely; very soft reaction to the accelerator pedal;
b. idle of very high quality. Vibration from the engine – zero, even for a cold engine. When sitting in the car, it is not possible to say, the engine is running or not;
c. reduced fuel consumption. Especially noticeable at speeds of 70 .. 100 km/h.
Finally, this engine works as it is supposed to! As the engine of the premium car should work.
It is interesting that BMW AG asked the dealer to store the solenoids from this repair.
I have to remark that the axis of one of the solenoids was mowing with jerks – it had significant wear. This is a substantial failure of the manufacturer! Slide bearing should be from the material, which does not give wear to the axis! I assume this wear could be one of the causes (especially by more considerable mileage and even if the oil has been replaced frequently).
Unfortunately, the valves were thrown in the bin, and I had no chance to look at them. Here: the picture of a new valve:
The diameter of the valve is around 12 mm, and the strainer is very, very fine! There is no doubt that this strainer will clog if the oil is not changed on time. Oscillatory jittering of the camshaft (before the repair) indicates exactly the clogging of this strainer – the reaction time of the valve is significantly reduced.