523i. Repair or loses?

Today’s patient – purchased recently, imported from another country. Unfortunately, the attempt to pass the TI was unsuccessful – the exhaust gases don’t correspond to the norm. The car received temporary permission for 1 month.


Part 1. TI. The protocol of the inspection

What does such a result mean?
Lambda = 1.00: the total (sum of both banks) fuel mixture is correct, the engine runs in Homogeneous mode, Stratified charge is not turned on (the reason could be some damages or the “choice” of DME – not yet a cause for concern).
HC is low enough (allowed norm: 200ppm), which means:

  • there is not mass misfires or no misfires at all;
  • CO catalytic converters work, at least partially (at least enough to pass the TI with a reserve).

CO indications are 2x above the norm (the allowed threshold: 0.2%), which means – the individual fuel mixture of cylinders is incorrect. So: not taking into account the correct average fuel mixture of the banks, in some cylinders the fuel mixture is lean, in some – rich.
Why so? Obviously, the engine has some problems with injectors or their adaptations, because normally working DME creates the individual adaptations of cylinders and compensates the differences of parameters of injectors (even half-working). Obviously, the differences in injector parameters are too large or – the DME doesn’t work as intended.
Of course, there is no guarantee, that during the time the DME will not record the error messages regarding CO catalytic converters, because of the requirements of DME to their performance are much higher (because the DME tests the CO catalytic converters in a partial load mode, not without load as in TI) than ones of TI, but the performance of the CO catalytic converters is sufficient to pass the TI. Such high content of CO in no-load mode means, that in real driving conditions the content of the CO in the exhaust will be several tenths of times above the allowed norm. CO catalytic converters are seriously overloaded and will get damaged very quickly!


Part 2. Repair of the “specialists”

The error message list – empty. Is it really everything in order?
Here, what the History memory indicates:

As you see, there are 3 sheets with a listing of the error messages. In addition, according to the odometer indication – most of them are very recent! There is no doubt – shortly before the visit to the service the error messages are simply deleted. Wonderful solution! Does it solve the problems? No, it doesn’t!

In the error message list, the error message 30EA appears for more than one time. What does this error message mean? The NOx catalytic converter is too contaminated. What do the BMW instructions (for example, ISTA Repair plan) say? The desulphation session should be activated and performed. Has somebody done that? No, they haven’t! Directly the opposite – when the error message is deleted, this problem is getting masked (the error message is not recorded repeatedly, but the problem doesn’t disappear), but the engine continues to work in emergency mode. It doesn’t use a Stratified charge, doesn’t perform the measurements of injectors, doesn’t create the adaptations, doesn’t clean the NOx catalytic converter. The consequences? Damaged NOx catalytic converter (cost of the spare part around EUR 2000); shivering of the engine, incorrect fuel mixture, after some time – damaged CO catalytic converters (cost of the spare part: EUR 1500); unjustified replacements of injectors (cost of set of injectors around EUR 1600) and, as we see, the car can not even pass the TI.

Here, the finished adaptations of DME: as we see, after deleting the last adaptations, the engine hasn’t worked in Stratified charge for one time. Adaptations of cylinders – not finished, the engine even has troubles with Lambda adaptations of banks (incorrect learnbits are marked with red):

Here – all measurements of injectors in Stratified charge – zero, or more exactly – they are never performed!

Previous “specialists” not only have not performed the intended service procedure but – they have done everything to hide the problem, and ever haven’t been able to perform the re-adaptation of the engine!

Here’s a note – the only INPA “see” this History list. Accordingly – nor “universal” services, neither BMW dealers will not even know, why the engine (if we assume, that they will be able to perform the re-adaptation of the engine) doesn’t restore Stratified charge and all problems continue.

Summary: the owner of the car has paid money (don’t be naive – nobody works without reward), but instead or repair got only additional problems! If the TI would not “press” and a correct repair strategy wouldn’t be performed relatively quickly, the consequences would be rough – several thousand EUR to repair a damaged exhaust system and unjustified expenses: changing injectors, Lambda probes, and other parts!


Part 3. Diagnostics (stage 1) and desulphation
In the History list, no error messages regarding NOx sensor can be found – looks good. But this sensor has several hidden defects, regarding which the error messages are not recorded, but problems – the same as in case of a completely non-working sensor.
During diagnostics, a range of specific requirements are fulfilled for the complicated NOx sensor to be switched in Online mode and would start to send the data.

This time good news – the sensor works! Yes, it is not completely new, but its indications – reasonably correct. It’s good news and by 100% confirm the initial assumption, that exactly the contaminated NOx catalytic converter is a culprit of the emergency mode of the engine. The bad news – the 30EA error message is seen for a quite long time; if the DME will detect, that the NOx catalytic converter is too weak, the error message 30E9 will be recorded – and “the party is over”.

Evaluating the performance of the engine, a permanent vibration can be strongly felt. The engine runs on “five-and-a-half” cylinders.
The rough run menu indicates complete chaos in the performance of the engine:

It is clear, that the problems ar at least with 2 .. 3 cylinders (on both banks). Unfortunately, it is not well understood, what is wrong with the engine – does it has any problems with the injectors, or – incorrect (or out of date) corrections are applied top them. Or both problems together. To continue the diagnostics, necessary service procedures have to be performed:

  • desulphation session of the NOx catalytic converter has to be activated;
  • the NOx catalytic converter has to be cleaned;
  • the engine has to be readapted.

After proceeding all service procedures, DME should restore a full functionality (including Stratified charge mode) and restore the measuring of the injectors. New and correct data of injectors will indicate, which injector is in good working order, which – is damaged.

Here, the desulphation session in progress: Lambda around 0.95 (it means, 5% of the fuel is burned in the exhaust), the exhaust temperature after the catalytic converters: 600oC.

The contamination of the NOx catalytic converter was reduced for more than 2 times, to 185mg:

Now it’s time to readapt the engine. According to the best traditions – first comes the flywheel adaptations, then – the fuel mixture.

Here: the engine has restored Stratified charge (and all cylinders in this mode even work correctly!):

Also, the data of the NOx sensor confirm -DME has restored a full functionality:

The first two (contamination of NOx catalytic converter and limp mode) problems successfully solved!


Part 4. Diagnostics (stage 2)
In this stage, 3 injectors with 3 different defects were identified.

First injector with a defect: cylinder No.4. Live data of the injector indicate reduced flowrate by medium loads:

Actual chemical tests of the injector in Homogeneous mode (logically) also indicate reduced flowrate, here, also in Stratified charge mode – reduced chemical efficiency of the cylinder (against two other cylinders of the bank):

Obviously, the injector is not opening completely (I assume, its nozzle is contaminated). Although the parameters of the injector theoretically still fit in the corridor, it’s clear, that the injector has serious functionality problems.

The second damaged injector: cylinder No.3.
Here, the correction applied to the injector in Stratified charge, idle. The injector leaks in idle too much. Although it works correctly in a range of average/large load, it can not be used due to leaking.

Third damaged injector: cylinder No.5. This injector has significantly reduced efficiency in idle. Here, Stratified charge data:

And here: mechanical efficiency of cylinders in Homogeneous mode.

Taking into account the problems of both modes, we have to conclude, that the problem of the injector is not bad atomization (leaking of fuel insted of mist-type injection) of the fuel, but it has an inappropriately long opening time (defect of the piezo element). Yes, the injector works correctly in medium loads (opens slowly, but correctly), but in idle in Homogeneous mode, DME is not able to manage it. This injector has to be replaced for sure.