The owner of the E series car, equipped with an N53B30 engine, approached me for help. This time the situation is more interesting by fact, that the owner of the car is technically educated – initial information was professional and exact. Therefore it sounded even more unbelievable.

The car has troubles with cylinder No.3.

Misfire counters counted large numbers of misfires – several hundred during each driving session, and exactly in cylinder No.3. In idle and on the go vibration can be felt.


What has been done to solve the problem?

For cylinder No.3:

  • the ignition coil has been changed;
  • the spark plug has been changed;
  • the injector has been changed;
  • compression checked – it is correct;
  • the engine – tried to re-adapt.

The problems continue. Rough run indicates reduced mechanical efficiency of cylinder No.3. In the error message memory, the error message 29FC: misfire of cylinder 3, is active.


It became very interesting to me.

Here, Rough run data – the engine is warmed up, Lambda probes are working.

With bank No.2 (on the right side of the menu) everything looks fine. Mechanical efficiency of all cylinders – similar. Bank No.1 (on the left side of the menu) has problems. Remember – in the Rough run menu, cylinders are displayed in firing order.

So, the order of cylinders of 1-st bank: 1/3/2 (from top to bottom).

As we see, cylinder No.3 really has significantly reduced mechanical efficiency (at least for 2 .. 2.5 times less than for other cylinders of this bank). The efficiency of cylinders No.1 and No.2 – identical and significantly higher.

Yet a notable nuance: Lambda probes of both banks indicate the voltage of around 2.00V, which means: fuel mixture of the bank is correct (Stoichiometric, Lambda 1.00).

Does really something inexplicable has happened to cylinder No.3? Let’s see data of the fuel mixture:

We will inspect this menu, also starting with the bank No.2 – everything looks correct for it. Offset type LTFT, Integrators, Multiplicative type LTFT – correct.

And again, there are problems with bank No.1. Offset type LTFT is -1.50mg/stk. This is a minimal available value! -1.50mg/stk means, that for all cylinders of bank No.1 the fuel mixture is reduced for around 30 .. 40%.

Nevertheless, the integrator is around -9% or around -20% against the Integrator of bank No.2.

The fuel mixture in all three (each of them) cylinders has to be reduced for 50 .. 60%, for the average fuel mixture to be correct? There is no smallest doubt, that injector os one (or even several) cylinder(s) leaks in closed condition!


Which cylinder(s) could be the guilty one(s)?

If the fuel mixture in the range of the whole bank is correct, the only option: in cylinders, which injectors are leaking, the fuel mixture is rich. In cylinders, which injectors are not leaking, the fuel mixture is lean. Of course, as the N53 series engine has 3 cylinders in one bank, the following situation can occur: injector of one cylinder is leaking strongly, other – leaking much less, in it the fuel mixture is either rich or lean, in the third cylinder, which injector is not leaking – the fuel mixture is lean.

In an extreme case – injectors of all three cylinders are leaking, but in any case – we can indicate the “most leaking” injector. Replace it, then evaluate the situation repeatedly. If necessary – replace the next one, which is damaged less. In such a way, step by step – we will reach correct Rough run menu and data of fuel mixture.

Before drawing conclusions in the current situation, let’s see other data of injectors. The good news – the (old) adaptations of the engine are deleted just now, it has started to create new ones. For some moment the engine has worked also in Stratified charge – measurements of the injectors are available.

Here, the data of the injectors in Stratified charge, in idle:

As we see, in idle for injectors of cylinders No.1 and No.2, a strong negative correction against the injector of cylinder No.3 (at least -2mg/stik). There is no doubt – both injectors (of cylinder No.1 and No.2) are leaking in idle. The injector of cylinder No.1 is leaking more strongly, although the correction (leaking) of the injector of cylinder No.2 is strongly above the allowed norm. Also – the winter is only coming. If the injectors leak such strongly for the warm engine, what will happen in conditions of cold start, winter?

Here, the data of injectors in Stratified charge, partial load mode:

The injector of cylinder No.2 indicates an incorrect flow-rate. One more confirmation for the damage of the injector of cylinder No.2.

Unfortunately, the injectors of cylinders No.1 and No.2 has to be replaced.


Several questions stay without an answer:

1. why the mechanical efficiency of cylinders No.1 and No2 (Rough run menu: cylinders No.1 and 5) is so similar? Both cylinders indicate identical efficiency! Coincidence?

2. What happened to the injectors of both damaged cylinders?


Let’s start with question No.2.

I didn’t have any information regarding the history of the current car, but, based on my experience, I sent a message to the owner of the car – I suppose, that these injectors have been replaced previously and used ones were installed. The reason – mileage of the current car is below 100.000km – it’s nothing for the injector. The injectors do not tend to “get damaged” massively! And, even more – directly in one bank.

After a short moment, I received the message from the owner of the car:

”1st injector – I’ve replaced with refurbished from eBay with test protocol. The test protocol is in all parameters OK ☹

2nd injector – was in car when I bought it, but was for sure changed, because it has index 06 and the rest of injectors has index 11.”

Both injectors are replaced! Both are replaced with used ones! And both – not working correctly! Once again I got a confirmation for what I said before – using “second-hand” injectors is a waste of time and money! Of course, it was nice to receive the confirmation of my assumptions. At the same time – I was not happy, because it was clear that the owner of the car can expect a bill or around EUR 500 .. 600.

Going back to the topic – how could be the performance of two damaged cylinders be so identical? The identical performance can mislead many diagnostics specialists: it would be logical to assume, that exactly the damaged cylinder is the one with different indications! The explanation is simple: if the fuel mixture is rich, the performance of the cylinder will be defined (limited) by the amount of air. The air will define, how much fuel will be burned. Leftovers of the fuel will get in the exhaust. As the amount of air sucked inside the cylinders is equal, their mechanical efficiency is also equal. Not depending on 5% or 35% left-over fuel will get in the exhaust. In the good cylinder is a deficit of fuel (its fuel mixture is lean). The performance of the good cylinder is limited by fuel – there is a lack of it, accordingly – the mechanical efficiency is reduced.

Here – the riddle is solved. Unfortunately, by using damaged injectors, a lot of time and also money is lost. The engine has been repaired for several (at least 3) times, a positive result is not reached.

Most probably, the correctly working injectors have been replaced by the faulty ones and the only problem of the car was damaged NOx system, due to this DME was not measuring injectors, did not perform required adaptations. Or even more simple reason – after some repair, the re-adaptation was not performed, the NOx catalytic converter was not cleaned in time. With each repair, the problems only increased. Now it’s time to do everything for good – replace the damaged injectors, perform the re-adaptation of the engine.