Possibly, it will be the most shocking entry. At least for me. But, as only during this week already three BMW owners had this exact problem, I decided to inform all owners of cars with N43 and N53 series engines.

Separate cases were known already before, also I have experience with the current problem (my experience – in the continuation), but looks that the problem is much more serious than it seemed before.


Symptoms of the problem:

the engine works normally in the Homogeneous mixture mode, but in Stratified charge – very roughly. Misfires are typical, the engine turns off Stratified charge, switches to Homogeneous lean fuel mixture (with Lambda around 1.50), but also in this mode, it will work far from perfect; tends to switch to Homogeneous work mode (full emergency mode).

In this situation, the owners usually have replaced the ignition coils, injectors, investing several thousands of EUR without success.

When inspecting these engines, I have to make conclusions, that the Lambda in banks is correct (it means, the proportion of the fuel mixture is correct), data of injectors in Homogeneous mode – correct (that would be quite strange if new injectors would be damaged).


Where hides the cause of the problem?

No matter how paradoxical it sounds – in the spark plugs!


How is that possible?

  • In many catalogs, these unique (N43/N53 series) engines are falsely included in the family of “ordinary” N series engines say – the similar spark plugs will be fine for them, just find the right ones;
  • in the market also fakes of spark plugs, intended for N43/N53 engines, are very popular – these spark plugs are expensive, selling of fakes – very beneficial;
  • also the sales persons of BMW dealers are making mistakes. Yes, exactly – and such situation is not rare, unfortunately.


Basic things, which you have to know about spark plugs for N43/N53 series engines:

1. there is only ONE manufacturer, who manufactures spark plugs for these engines: NGK

2. there is only ONE type of these NGK spark plugs: High energy

3. there is only ONE model of these spark plugs: NGK ZKBR7A-HTU


Why are these spark plugs so unique? The air gap of these spark plugs is increased – it’s around 1.2 mm (for usual spark plugs – around 0.6 .. 0.7 mm), so the fuel can be ignited in Stratified charge mode. The spark plug has three side electrodes and one central – it’s very important in case of multi-ignition.

Multi-ignition mode – in every injection cycle MSD performs several “attempts”. These several ignition events allow burn the fuel better and also solves problems with misfires if the first attempt to ignite the fuel was not successful.

NGK spark plugs are made in such way, that the central electrode burns from sides, which prolongs the lifetime of the spark plugs for 3 times (comparing to spark plugs with one side electrode).

These spark plugs can manage voltage two-three times higher and the energy of spark 3 .. 4 times higher than for regular spark plugs – that’s the reason, they are called High energy. In the same time – their physical size is the same as for “regular” spark plugs. It means – the insulation, precision of assembly, quality of all materials – requirements are much higher! It makes these spark plugs so expensive!


One more important nuance, how the performance of spark plugs for N43/N53 engines differs from “regular”(no direct injection – Stratified charge) N series engines:

  • in case of Homogeneous mode the fuel mixture is injected as for “old” engines – in the expansion cycle, then – the fuel mixes with air and it is ignited in the necessary moment. For N43/N53 series engines this mode progresses as for “regular” engines – so also in case of inappropriate spark plugs, the engine will be able to perform more or less satisfactorily;
  • in Stratified charge mode, used by BMW AG, the fuel is injected right before the ignition! In this mode increased power of the spark is necessary – “regular” spark plugs cannot provide such high energy of the spark! Even more – the location of the spark has to be ensured with high precision, till few-tenths of a millimeter, because the fuel mixture around the spark plug (and the injector) is very uneven. If the spark will be even one millimeter too far – the mixture would be lean, a misfire would be inevitable. If the spark would be even one millimeter to close to injected fuel – the spark plug will be moistened with fuel, and also in this case – misfires would be inevitable!


Here, the image of BMW AG, how important the injector’s beam opening angle is:

As you see, even small differences from ideal spray cone are not acceptable! The location of the spark has the same high requirements!


Differences of inappropriate spark plugs:

  • the power of the spark is too low for Stratified charge and is not able to ignite the fuel in this performance mode;
  • “location” of the spark is for at least several mm different from necessary – the fuel cannot be ignited in any way;
  • the spark plugs are not intended for multi-ignition mode and are wearing out very quickly;
  • the spark plugs are intended for totally different thermal conditions, in the existing conditions they are performing totally incorrect (even in case of Homogeneous mode, taking in account the compression of N43/N53 – 12:1; active usage of EGR).


Where to purchase spark plugs, intended for N43/N53 series engines?

I say – buy them only by the dealer!

Unfortunately, as if respectable companies, who sell BMW products, tend to sell (possibly, even not knowing about it) fakes. Very often these fakes cost almost the same as OEM spark plugs – it gives additional credibility.

Yes, these spark plugs are not cheap, they have to be replaced quite often (after several tens of thousand km), but – even one unjustified visit in the service center will cost more expensive! Not even talking, that in the service you can be convinced, that the ignition coils and injectors are ones to blame: the replacing of them will be much more expensive! And even harder – the working parts will be unjustifiedly replaced, and additionally – there will be no improvements! And the service specialist would perform in full confidence – such, as if simple, the cause of defect would not even come to the mind!


How to recognize original NGK High energy spark plugs!

1. the spark plug has three side electrodes;

2. the logotype of the spark plug is painted on the insulator:

a) NGK spark plugs, which are sold as BMW product

b) NGK spark plugs, which are sold as aftermarket product:

additionally, the logotype is painted under the layer of the varnish, not on top of it. It cannot be easily scratched off or washed off, it’s contoured look slightly fuzzy, but the color – not bright.


DON’T BUY the “NGK” spark plugs if the logotype is not painted on the spark plug itself! No, the cardboard box, which costs 0.1 cents or a “certificate” – a cheap sheet, which says, that this is NGK spark plug, DON’T confirms, that this is an original! These are top line spark plugs of NGK – they are not produced in different factories, in a “happy-go-lucky” way!


My personal experience is quite sufficient:

I have made sure myself, that large company in our region, which is specialized exactly in BMW products, sells “NGK” spark plugs without logotype on the insulator for a high price (only EUR 0.50 cheaper than BMW dealer). NGK is mentioned only on a low-quality cardboard box. When I started to show interest regarding the origin of the product, the seller confessed, that they bought “leftovers” from not the widely known wholesale company for the very good price.

I have made sure myself, that in the official BMW service center the service specialist offered “iridium” or “platinum” spark plugs after checking the engine code and VIN and is ready to sell them to the customer. When I asked the sales manager, how is that possible, he made excuses, that, probably, the current vehicle has options, according to VIN. When I specified VIN number repeatedly, the manager honestly confessed, that, obviously, has mixed up – most probably he made a mistake when previously entered the VIN in TIS system.


Be watchful – the performance of spark plugs is critically important for the performance of each petrol engine! And for the N43/N53 engine, it’s mega-important!