This time – quite an untypical case: the owner of the car did not have any complaints regarding the performance of his engine, but he reached out to me with a request to perform the engine diagnostics. The cause was logical and justified – check if the engine does not have any problems in the initial stage and, if necessary, solve them before they have progressed and caused more considerable expenses.
The vehicle: G30; sold at the beginning (March) of the Year 2018. B58 engine, the actual mileage around 100’000 km, the average speed around 50 km/h (the same was at the moment of purchasing a car with a mileage of 86’000 km).
By such speed, 100’000 km means around 2000 motor-hours – it’s actually just a “warm-up” resource for the BMW engine! Everything should be perfect!
This time I will miss the “not interesting” part. I paid particular attention to the specific problems of the B58. No error messages were recorded in the DME error message memory regarding the engine’s performance. All live data were correct.
We started with idle. Here is the mechanical efficiency of cylinders in idle:
Unfortunately, the efficiency of the 1st cylinder is slightly reduced (blue curve, its average value is 1 .. 2 points above 0). Typically this problem appears due to rare oil changes (first cylinders – “further” from the oil pump – are experiencing air “starvation” due to HVA problems). The situation is not (yet) critical, but it is not ideal either – DME has not managed to even out the mechanical efficiency of cylinders. So: update the software; re-adapt the engine – then re-evaluate the situation and change the oil as often as possible in the future! For my car, in suspicious cases, it helped to raise the level of IL (Integration Level) and re-adaptation of the engine. This time it is worth raising the level of the IL because it would solve the problem of the cooling blind (there was an error message in the error message memory).
Next hub, worth the attention: VANOS: Here is the required (red) and actual (green) position of the VANOS inlet shaft:
The actual position differs from the ideal by around +/-1.5 degrees.
A slightly better situation is with the exhaust VANOS. In the image: required (grey) and actual (yellow) position of the exhaust camshaft.
The exhaust shaft’s position differs from the ideal even till 0.9 .. 1.2 degrees.,
During transition processes, the exhaust VANOS behaves much worse:
We see that the short-term position difference reaches even +/-7 degrees. For example, around the 27th second!
The PWM jitter of both management solenoids of both management valves is increased (up to +/-5 .. 6%). Tests were completed successfully, but – with (my) comments.
During tests, the VANOS is turned in the range of 60 degrees. DME measures both – short-term and long-term – differences between the required and actual position. During tests, the acceptable short-term error is +/-5 degrees. In the menu, it could be clearly seen that the jitter of the position reached even +/-3.5 degrees, which is quite close to the allowed border. Now it is time to remark that the VANOS of the new engine maintains the required position in a range of +/- 0.5 .. 1 degree. Also, the PWM jitter of the valve solenoids is much lower. What conclusions can we make? Obviously, even in the case of a perfect driving profile, the 30’000 km oil change intervals (and even only one or two oil changes) are doing noticeable harm.
What to do in such a situation? Change the oil as often as possible. Unfortunately, the only thing that can be done – is to slow down the progression of the problem. The situation is not pleasant because there are no official confirmation of the problem and a repair by the warranty can’t get, because formally, the tests are successful. It would be useful to repeat these tests after some time (for example, once in 6 months). If these VANOS tests “drop” with the error message at any moment, you can approach the dealer with a reclamation – the hub is malfunctioning.
The last comment is very far to till the recording of the error message. For the error message regarding VANOS to get recorded, the mismatch of the positions should be 4 times larger than in the performance tests (+/-20 degrees). Such a significant problem should last at least 1 .. 3 seconds. Bosch DME is not the most active one in recording the error messages…
Next hub: Valvetronic
Here everything is fine. The position of the rotor (blue color, bold) is stable; DME does not try to correct it nonstop. The last upgrades (forcible oiling of the worm gear; adjustable teeth gap) have given the result.
The last object of the inspection: is the ignition system. First – is the performance of cylinders in unfavorable conditions.
In the image – the performance of cylinders by very low required torque (accelerator position around 10%, red curve). Everything is fine – the spark plugs are not “clogged” by the carbon residues. The owner of the vehicle confirms – he just got back from a long ride on highways. More significant load to the engine – best self-cleaning of the spark plugs.
Next stage – inspection of the misfire counters.
With red, more extended counters, different from 0, are marked. In addition, such data are gathered just starting the new driving session. So, when the previous driving session was finished, these readings were 2. Such value means that during the last driving sessions, in these cylinders, several tens of misfire evens (on average) were detected! There are problems!
After a test drive of 15 km, the misfire counters indicated:
Here, 2 events are registered for the 5th cylinder. Obviously, the defect/problem is sporadic because 2 events (just 2 events; just in one cylinder) are not enough to confirm the problem. True though, during the test drive, when accelerating with 2nd gear with increased required torque (subjectively – some 200 .. 300 Nm), I clearly felt some group misfires (5 .. 7 .. 10+events) in one of the cylinders. Unfortunately, as it suits Bosch DME, misfires were not identified (obviously, their detection in this driving/transient conditions is disconnected).
This ignition problem should be solved ASAP. Good news – the ignition coils are not expensive: around 50 .. 55 EUR (OEM; Bosch; NGK).
The owner of the car sent me the images of old spark plugs (he had replaced them directly after purchasing the vehicle):
All spark plugs looked like that – they are entirely brand new! Obviously, they were replaced directly before selling the car. A logical question – who changes the spark plugs before SELLING? Normally – no one (let’s be honest). If only – there were error messages regarding misfires and/or intense shivering of the engine (which could be assumed as a defect). Yes, such a scenario is plausible because quite often, I have “met” BMW petrol engines, whose spark plugs were “exploited” for 80 .. 90 .. 100.000 km, ignoring the misfires – severe shivering of the engine and the “popcorn” from the exhaust.
The lousy news: The ignition coils are damaged due to worn-out spark plugs. You are saving on replacing the spark plugs, but you will also have to change the ignition coils. This time – observe misfires and their counters; if it is not possible to do it regularly (and got repeated/100% confirmation of the problem), the ignition coils of the suspicious cylinders should be replaced.
Spark plugs, which are not replaced in time, damage both ignition coils and the CO catalytic converters. Don’t try to save money on the ignition system!