In this entry – a diagnostics situation seems very simple at first sight. Even too simple.
N43 series engine. Error messages, recorded in the DME error message memory:
29CE misfirings, cylinder 2
2A2C fuel mixture control 2
Unfortunately, no freeze-frame data because the simplest solution to problems – deleting the error messages – is used. No error message, no problem.
But, the symptoms are still there. The engine vibrates in ide.
Let’s see the performance of cylinders:
Marked cylinder: No.2 (by placement). The efficiency of this cylinder is strongly reduced. Only one-half of the necessary. In this menu, cylinders are displayed in the firing order, which means 1/3/4/2. Other cylinders are working identically – obviously, they are in perfect order!
At first glance, the problem seems solved: there are error messages regarding cylinder No.2, and the 2nd cylinder is actually performing poorly. And additionally, the fuel mixture in both banks is correct (bottom line of the menu, the voltage of the Lambda probes – very close to the perfect 2.00 V). What happened to cylinder No.2?
But, if everything had been so simple, I would not make this entry.
Let’s see what happens with the fuel mixture. There are error messages in the DME error messages memory also for it.
Already in the first picture, we see serious problems. There are two of them:
a. LTFT Multiplicative type adaptations are close to minimum (-30%);
b. STFT or Integrator is close to minimum (-30%).
Both problems are present precisely in the second bank. The second bank, as we know, is cylinders No.2 and No.3.
And here is the 3rd problem, exactly for the 2nd bank:
LTFT Offset type adaptations have reached the minimum (-1.0 km/stk).
What do these numbers mean? One of the injectors of the 2nd bank is leaking. Leaking strongly. DME has reduced the fuel supply, using all available LTFT tools (both Offset and Multiplicative types/low load); even the Integrator is close to the minimum and gives an additional fuel amount reduction of 25%. Despite the drastic measures, the fuel mixture in both banks is correct (as we see in the first image)! Is something wrong with LTFT? Does DME lie?
What do the live data of the injectors say?
In this menu, the injectors are displayed in the following order: 1/4/3/2
As we see, the injection times of the 1st bank (No.1 and No.4) are almost 2 (!) timers longer than for the 2nd bank (No.2 and No.3). Live data confirm that the fuel injection of the 2nd bank is indeed strongly reduced. 2 times shorter injection times, but the fuel amount injected is as necessary? Here, a 100% proof that one of the injectors of the 2nd bank is leaking.
Possible scenario – for example, the injector of the 2nd cylinder is leaking. It sounds logical. There are error messages regarding this cylinder; it really “drops out” against the other cylinders.
No, this time, the situation is different.
The performance of the 2nd cylinder is reduced because it has not enough fuel! It is only logical – the fuel supply to this cylinder is reduced by almost half! It is only logical that the performance of the cylinder is reduced by half. The injector of the second cylinder works correctly! The fuel mixture in this cylinder is lean – no wonder it catches misfire.
Instead, how is that possible that cylinder No.3 works “on full power”? There is only one explanation – the injector of this cylinder is leaking! Although the injector opening times are reduced 2 times, this cylinder has more than enough fuel!
Conclusion: cause of all problems – the leaking injector of cylinder No.3
Yes, sometimes the situation turns out more cunning than it seemed initially. Therefore always, all data should be analyzed and made sure there are no contradictions.
