My experience with BMW engines is more than 25 years. So I don’t complain that B58 has a lot of “adventures” because – what can be worse than boredom? This entry can be considered as a continuation of this entry.  

It’s not like the previously described crash in idle was utterly unexpected. Lately, I have noticed that the engine performance has become more jerky. Harsh misfires could not be felt, but the performance of the engine was not perfectly smooth. But the most significant change I have noticed – popcorn (in Sport/Sport+ mode) has become much more obvious and loud. There were such loud explosions that I did not feel very comfortable when driving in the city. Loud popcorn can be heard even by switching gears and driving relatively calmly!

Already before, I have observed – when the spark plugs are replaced, the popcorn becomes significantly quieter. These changes (because worn-out spark plugs are replaced with new ones) are fundamental! Taking into account all the symptoms, it was clear – there were severe problems with them, and the replacement was already planned. But, till the replacement, I had spare time for some experiments. The initial purpose of the experiment is to check, more in detail, how this DME handles the recognition of misfires in idle. 

When opening ISTA, a surprise was waiting for me:

What happened to the catalytic converter? Just 10,000 km ago, it was in perfect technical condition! TI was not able to measure HC or CO – both parameters were 0 (both in idle and by 2000 RPM)! Mechanical damage? Melted due to a leaking injector or fuel mixture problems? No, such problems weren’t noticed. The cause of the problem is not to be looked at – misfires, due to which the catalytic converter is overloaded. The fundamental impact of the misfires on the tests of the catalytic converters I’ve observed already since the N53 series engine generation. True, though, in that engine generation, misfires were recognized quite well, and the owner of the vehicle was warned (especially in the E series). In addition to recording the error messages, other measures were taken too – the injection method was changed (DME switched from Stratified charge to Homogeneous lean, from Homogeneous lean – to Homogenous mode). How is Bosch and B58 doing with this issue? Quite bad, because I can feel the jerky performance of the engine, I can hear a very loud “popcorn” (it is not even a popcorn – real explosions can be heard), even the crash in idle happened, but – there are no error messages regarding misfires in the DME error message memory! 

In several entries, I have mentioned Siemens patent, which intends that the misfires are detected by the changes in the flywheel acceleration. Initial patent: WO1993021508A1. Although the patent is ancient (submitted around the Year 1993) and has been terminated in many countries (FR, GE, ES, and others), WO (PTC) – the world patent is still valid! It would be interesting to find out how Siemens has managed to “stretch” this patent for so long!

Considering the situation with this patent and the fact that this Bosch DME does not identify misfires in idle (confirmed by practice), three options are possible:

a. Bosch has not purchased the license from Siemens and decided to “save some money”;

b. Siemens has set unrealistic conditions for the purchase of the patent rights or refused to Bosch the use of this technology;

c. Bosch believes that their own patented principle – detecting the misfires by using the accelerometers – is enough.

At this moment, I have a question for BMW AG. Gentlemen, it’s Year 2023. Already, for 30 (!) years, an efficient technology to detect misfires is known. But in your premium segment cars, this technology is not used because the patent forbids it or the executor decided to “save some money”! How the terms of reference were drawn up? How is it possible that such important functionality was not a “must have”? Siemens asked for an inadequate payment for their work to equip your cars with their DME? I doubt it because equipping millions of BMWs is a “sweet” enough contract. Did you decide to save several Euros on each car? “Missed” such a “small thing”? 

Returning to the exact car/situation. Let’s see what ISTA says: 

Here, not a word regarding misfires! Only – the visual inspection of the catalytic converter and its inside. And even by these test points, I have questions:

a. if any visual damage to the body and/or active zone is identified, the catalytic converter has to be replaced. Logical and justified;

b. if such damages are not detected, but the error message is recorded, the catalytic converter is still recognized as damaged and has to be replaced. 

A question: why waste time and customers’ money (by inspecting the catalytic converter) if the catalytic converter still has to be replaced? 

In ISTA, it is mentioned that the error messages of the catalytic converter can cause fuel mixture problems and the error messages regarding it. Therefore, if there are error messages regarding fuel mixture, these problems should be solved first. I do have some comments:

a. what about incorrect fuel mixture in cylinders (but correct average fuel mixture)? It is self-explanatory that in such a situation, the CO catalytic converter will be overloaded. The problem is that for the increased difference in mechanical efficiency between cylinders, even the error message codes are not intended!

b. increased VANOS and/or Valvetronic position jittering, or the jittering of the fuel pressure – also, in this situation with the average long-term fuel mixture, everything can be perfect, but in the short-term – there will be serious problems. And again, no error message codes even intended and – no error messages, so everything is perfect?

c. my favorite topic – misfires! Even if there would be some error messages regarding misfires mentioned, there is nothing mentioned regarding the impact of this problem (misfires). 

At this moment, I have to conclude that serious problems have affected not only the technical part of the car but the creation of the documentation. 

Returning to the misfires. Let’s check the overall situation. As we know, ISTA would not be a help; let’s check OBD Mode 6:

As we see, there are “problems” with all cylinders. It is not a surprise because the car is equipped with a manual gearbox. The problem is described here.

This time, I checked if any cylinder was dominating. No, as we see, all cylinders behave similarly. So – the damaged ignition coils or some spark plug are not to blame.

As part of the experiment, I decided to check how DME reacts to misfires, which are created by the defect of the ignition coil. As the example here suggests, misfires created by the flooded spark plug in idle DME are not registering at all. What will happen in a simpler situation? 

First: live data of the working engine:

I marked/selected the mechanical efficiency of the 1st cylinder, too. As you can see, it is perfect. Now we disconnect the ignition coil of the 1st cylinder:

As we see:

a. mechanical efficiency of the cylinder is around +60 units; the cylinder is really turned off;

b. misfire counter swiftly counted 95 misfires after his “froze” for several seconds;

c. DME has switched off the injector of the 1st cylinder, Lambda, around 1.25. 

After several seconds:

Here, all cylinder misfire counters are 0! Even though the engine continues to work on 5 cylinders (it can be seen by Lambda 1.30)! This time I know which cylinder is “damaged”, but – what to do if the diagnostics specialist does not know the defect?

The only comment regarding this – is the clumsy addition of an already clumsy solution. In the situation when the cylinder is turned off due to misfires, show the misfire counter as 0 – excellent! If there are no better ideas, I offer:

a. leave the last value by which the cylinder is switched off (by this indicating that this cylinder had problems);

b. replace 0 with the record “cylinder disabled”.

Could it be that such experienced companies as BMW AG and Bosch, who have been working with petrol engines for many decades, did not think of something like that?

At this moment, I decided to check the error messages recorded in the DME error message memory:

No error messages recorded in the DME? There should be something! True, though, the error message list is not upgraded automatically. Not even for those blocks, which are checked during call-up functions. It is not even possible to perform a quick error message list refresh for some exact modules. 

I turned off the engine. After repeated reading of all blocks:


a. the connection of the ignition coils is not controlled for this DME! This is only the SW question because there already is the hardware to control the voltage – with its help, the Combustion length is measured;

b. DME identifies incorrect Combustion time. The error message 150102 is recorded correctly. Better than nothing: 

c. the error message 140110 is “fake”. More precisely – this error message is not exactly identified but (this time) is recorded as a logical consequence of 150102;

d. the error message 140101 is a consequence of 140110. Unfortunately, even till this moment, BMW diagnostics does not intend a correct system that would notify the diagnostics specialist – this is the “event”; these are the “consequences of error message X”, etc.;

e. 140010 and 140001 makes me ask some questions. DME has identified “several” cylinders, which have misfired? “Several” cylinders are switched off? I was observing the misfire counters for all this time. Except for the 1st cylinder, all were 0. Lambda around 1.25 .. 1.30, which confirms that only one cylinder is switched off. How do we understand this?

f. 120408 error message – here we see a remark: as a consequence. True, though, every decision to switch off any hub or functionality – these are consequences. 

On the navigation system screen, the message appeared:

At the same time, the Check Engine sign did not light up in KOMBI!

In several cylinder misfires are identified, several cylinders are switched off, turbo aggregate is switched off, but – no need to light up Check Engine? Impressive!