This will be a case of an all-time-ever unpleasant experience. Of course, some other case will replace it eventually, but for now – enjoy.
Some time ago, one of N53 series user from Ukraine asked me, if I had encountered quite a peculiar situation. And now I can say – yes, I do!
Patient: E60, N53B30.
Description of the problem: driving evenly, for example, 90 km/h, no problems observed. The engine correctly performs in Stratified charge mode. But, if there are any hump and the required torque increases, the engine of the car suddenly starts to perform very unevenly. The fuel consumption indicator shivers for several seconds, then it calms down, but the engine continues to run in Homogeneous mode for a while. Needless to say – the fuel mixture, test data of the injectors – correct.
In my case the problem, mentioned above, was supplemented by the detonation of one cylinder in exact driving modes. For example, in 1-st and 2-nd gears, while accelerating with an average required torque. Detonation could be heard as “clack/clack” sound. So loud, that it could be heard inside the car, with windows closed. When connecting the INPA, I concluded, that the detonation was present only in Stratified charge and Homogeneous lean modes. If allow the engine to run in such mode (detonating cylinder), after several seconds the MSD switches the engine to Homogeneous mode – also the DME detonation sensors inform DME regarding high detonation. It’s clear the detonation is very dangerous to the engine. The detonation is an avalanche-type fuel burning process. The pressure in the burning camera increases rapidly, and its max value is significantly higher than in a normal situation. Detonation is a common cause of mechanical damages of the engine.
During the time, the DME created adaptations of very late ignition (later ignition – one of the ways, how to avoid the detonation), but it didn’t help. Some of the cylinders continued to detonate, the engine became very unresponsive.
After a while, the engine turned off cylinders No.1 and No.6 for several times. It’s interesting the EML indicator was not lighted up, and the engine continued to work on 4 cylinders.
Here, the error message regarding disconnecting the cylinders due to incorrect performance:
As we see, the engine has performed in mode 3: Stratified charge. It’s interesting in the attributes of the error messages is not indicated, which of cylinders has been disconnected! It makes it very difficult to indicate the problem.
In one of some 10 such cases the following error message was recorded:
Here – the cylinder No.6 has been disconnected. A good start, but only one problem – the injector of cylinder No.6 has been replaced recently, the spark plug and ignition coil are completely new!
At the same time, live data confirm the cylinders No.1 & No.6 are disconnected! Why is the cylinder No.1 also disconnected? Obviously – to allow the engine to work more or less normally.
Assuming, that the cylinder No.6 (and not No.1) was disconnected due to incorrect performance (misfires), additional attention was paid to the 2-nd bank.
Live data confirmed the cylinder No.4 has increased multiplative type fuel correction.
The data of chemical tests of the injectors in Homogeneous mode indicate large differences of efficiency of injectors for 4-th and 5-th cylinders.
Here, in idle (Stratified charge) the opening times of injectors of cylinders No.4 & No.5 are reduced, but in the condition of average load – the situation is even quite correct.
Rough run data sometimes indicate increased mechanical efficiency of cylinder No.4 (by placement) in Homogeneous mode, but in Stratified charge mode – everything is correct.
At the same time, the following problems are observed:
a) the error message regarding decreased efficiency of the catalytic converters is recorded regularly (both in Homogeneous and Stratified charge mode), in addition – these error messages are chaotically – for example, in Homogeneous mode the problems are as if with the catalytic converter of the 1-st bank, in Stratified charge – with the catalytic converter of the 2-nd bank. After a moment – the situation is the opposite;
b) the error message 3104 appears regularly, the engine performs in Stratified charge for a little while, then switches to Homogeneous lean mode; at the same time – the fuel mixture of the banks is correct;
c) the detonation problem is present both starting the driving and driving evenly – but only with required torque above 50 .. 70 Nm (Stratified charge and Homogeneous lean mode);
d) appears even 2A2D (reduced fuel pressure in the low-pressure contour), later also 29F2 (reduced pressure in HPFP contour). Obviously – some of the injectors pours out an inappropriately high amount of the fuel;
e) the error message 2D64 appears – MSD has troubles to maintain the Homogeneous mixture.
At the same time – outside the critical mode, everything looks acceptable. And, as I already mentioned before – all possible components (the injector, the spark plug and also the ignition coil) of as if damaged cylinder are with the less wear, comparing to the other cylinders.
Some more “great” news: MSV70/80, MSD80 DME has no access to the detonation data! Not even talking regarding detonation of each cylinder – even the average data of each of 2 sensors are not available (that would allow evaluating the average detonation level of the bank). Nor INPA not ISTA can help in this situation. Also, sequential disconnection of cylinders didn’t help to identify the guilty cylinder. Disconnecting any of cylinders, even when the engine worked in Homogeneous lean mode, the detonation disappeared. The reason – when disconnecting the cylinder, DME turns off the integrators and, obviously, also many more fuel adaptations (for example, LTFT of the banks) – it was enough for the problem to disappear.
At this moment it’s worth to mention the basic information regarding cylinders 4/5/6 (assuming, that the problem is in 2-nd bank). It is possible – due to some other incorrectly performing injector the fuel mixture in cylinder No.6 becomes too lean and creates misfires.
Cylinder No.4: injector release – No.7, resource above 300’000 km;
Cylinder No.5: injector release – No.11, resource around 100’000 km;
Cylinder No.6: injector release – No.11, resource around 10’000 km.
The injector of cylinder No.4 looks more suspicious. The largest wear, the largest difference in the chemical tests.
Replacement of the injector didn’t improve the situation. Yes, (after re-adapting the engine) the large differences in the chemical tests disappeared, but the detonation problem was still there.
Next in line on the suspicious injectors: cylinder No.5. This one also (the same as No.4) slightly leaks in idle, wear – next in the list. Unfortunately, the replacement of the injector didn’t solve the problem.
And the last hope – replacement of the injector of cylinder No.6. After replacing the injector – yes, all the problems disappeared! But the injector has been used for only 10’000 km! The problems appeared several thousands of km before. Such specific defect already after 7.. 8’000 km!
Here is another confirmation – the defects of the injectors are not directly dependent on wear! It makes no sense to replace injectors just because they have already served 100.000 or 150.000 km. It is strange, but seams, that the injectors of older releases tend to serve (averagely) longer time! It looks that the quality of injectors is going lower with a newer release…