This entry is – a summary after diagnostics and repairs of several thousands of N43/N53 series engines. 

Description of the situation: after restoring the Stratified charge, the shivering of the engine can be felt. Exactly shivering/jerking (short-term unevenness of the performance), not, for example, permanent (monotonous) vibration.

A myth. At first, I will dispel one myth, which sometimes appears in the environment of unqualified personnel. There are “specialists” who blame the NOx system in this situation. Because when disconnecting the NOx sensor or paralyzing its work in any other way (for example, connecting a non-working sensor), the shivering of the engine disappear. 

Such a statement is not valid. DME uses the NOx system for only one decision: allow or restrict the Stratified charge. If the Stratified charge is authorized, DME uses the data of the NOx system to “decide” how often the NOx catalytic converter should be cleaned (regen and desulfation sessions requested/performed). And that’s it! All other decisions – when and how much fuel to inject in each cylinder; how wide open the throttle; when to ignite the fuel, etc. – are made by DME itself, without any use of data of the NOx system. It means there can not be a “more even” or “more uneven” sensor. 

Such a test of “turning off” the NOx system can confirm only one thing – the engine has problems exactly in Stratified charge mode. But the NOx system is not the one to blame! Directly the opposite – the NOx system has ALLOWED use of the Stratified charge! Everything is fine with the NOx system!

What are the most typical reasons for uneven performance in Stratified charge mode?

a. regular/often misfires in all cylinders: use of wrong spark plugs. Relatively often problem. In many catalogs, Bosch spark plugs are indicated as analogs. Unfortunately, these spark plugs are not suitable for the Stratified charge mode! For more about spark plugs, read here and here. Not so often, but it happens – fake NGK spark plugs. Don’t buy cheap spark plugs, even from a reliable wholesaler. It is worth purchasing the spark plugs directly from the BMW dealer; they will serve longer. Important: in Stratified charge mode, more considerable energy (“spark”) is necessary to ignite the fuel than in Homogeneous mode. Precisely, for this reason, Bosch spark plugs or worn-out NGK spark plugs will more or less correctly perform in the Homogeneous mode, but they will fail in Stratified charge;

b. ignition coils. I don’t suggest using Delphi ignition coils. About problems with these ignition coils, read here and here. One more nuance – use Bosch ignition coils with only indicated code (0221504471)! In the catalogs, another Bosch ignition coil can be found – a newer version, as if analogs, but according to reports from the users, in several cases these ignition coils were the cause of mass misfires. These “analogs” may have other parameters (smaller transformation coefficient) and are mistakenly indicated as a complete analog. Important: in Stratified charge mode, significantly (3 .. 4 times) larger energy of the spark is necessary than in Homogeneous mode. For this reason, the quality of the ignition coils has a crucial meaning! Ignition coils, which can ignite in Homogeneous mode, can fail in Stratified charge;

c. injectors. In Homogenous mode, the fuel is injected a long time before igniting. Even poorly injected fuel has enough time to mix with air. Even if the fuel has hit the spark plug, the spark plug has enough time to dry. The fuel in the combustion chamber is rich enough for the fuel to ignite. In Stratified charge mode, the situation is much more complicated. The fuel is injected and ignited at the exact moment. It has no time to mix with air. So – the fuel mixture in the place of the spark should be rich enough to ignite. If the injector makes even a slight “mistake”- inject the fuel slightly too far from the spark plug, the fuel mixture will not light up. If the fuel hits the spark plug, it will not ignite either because the spark plug will “drown” (it will have no time to dry). Finally – the injector should inject the fuel as a little fog for it to ignite. The reason is the same as previously – the fuel has no time to evaporate and mix with the air (directly opposite as in Homogenous mode). Due to all these reasons, the engine may be more or less OK performing in Homogenous mode, but in Stratified charge, misfires start. More about injector problems, read here (relevant: third and fourth scenarios). 

Note: if the injector is damaged, its defects will not disappear, even if the engine uses only the Homogenous mode. Even if no misfires are detected at the moment, the problems will manifest themselves. Poor atomization – the piston can melt; the fuel burns poorly – a massive load to the CO catalytic converters (and their shortened lifespan or even quick damage). Incorrect angle of the beam – in this case, the fuel burning is erroneous. Unfortunately, these engines have no perfect mode, which could ignore the injector problems. 

Usually, the unevenness of the engine in Stratified charge is confirmed with the error message 3104. N53 series engines (especially – older releases of SW/ZB) are recording the error message 3104 very actively, even due to uneven roads. BMW AG solved (tried to solve) this problem (uneven run and fake 3104 errors) several times by updating the software. More about it read here. A fundamental improvement: DIRU upgrade, read here. Summary regarding 3104 error message read here

The first step, what I suggest to do if you feel the uneven performance of the engine, but the basic things (ignition coils and spark plugs) are new: check the misfire counters. How to do that, read here. Nuances strictly for the Stratified charge are described here.

If you follow the previously mentioned instructions step by step, the engine of your car will work perfectly. There is no place for guessing or visual inspection. Visual inspection of the ignition coils or the injectors will not give anything; the data of the injectors should be evaluated via INPA and misfire counters – via OBD Mode 6. Only technical data will show the actual situation.