“Hero” of today’s story – N53B30 O0.
A few months ago during the longer driving session, uneven performance of the engine was observed. Inspection of misfire counters with the ELM327 adapter was detected, that there are increased count or misfires in cylinder No.6. In longer driving session (more than two hours) the misfire counter identified 30 events, between-driving sessions counter showed 5 events.
Replacing the ignition coil as if helped (the resource of the ignition coil was around 150’000 km, which is quite long if we take into account the specific to the ignition system of this engine). For next month the misfire counters were very close to 0. After a month, the misfire counters in cylinder No.6 started to increase. As it nothing special – around 5 .. 10 events during a one-hour long driving session, but in several modes, the engine behaved quite strange – as if working with 5.5 cylinders. In the same time – integrators and LTFT (both offset and multiplicative) were showing exact “picture”.
Today – unexpextedly the misfire counter for cylinder No.6 increased, and also additonal symptoms appeared:
a) offset adaptations for bank No.2 suddenly dropped from +0.7 mg/stk to -0.3 mg/stk (offset for 1st bank’s LTFT was around +0.8 mg/stk);
b) multiplicative adapation of bank No.2 dropped from +17 % to +12 %;
c) Rough run data for Homogeneous mode are showing (according to firing order; cylinder No.6 according to placement) increased the efficiency of cylinder No.4, which was not converging;
d) individual adaptations in idle in Stratified charge mode were showing -2.5 mg/stk for cylinder No.6, but positive correction for cylinders No.4 and No.5;
e) if the Stratified charge was turned on in idle, the opening data were showing decreased opening time (almost for one half: 0.1 ms as opposed to 0.2 ms for other cylinders) for cylinder No.6. In the same time – Rough run data still are showing the increased efficiency of cylinder No.4 (according to firing order; No.6 – according to placement).
MSD80 has created incorrect adaptations after previous misfires? A mistake in the software? Does the injector cylinder No.6 has started to inject inadequate (increased) amount of fuel?
Immediately the standard procedures were performed:
a) deleting of all adaptations of the second group: ../F8/F2/Shift + F9;
b) creating new adaptations of the flywheel;
c) several short driving sessions for creating new initial adaptations performed.
Here are the images, what was the result of it.
1. It is strange, that MSD stubbornly refused to confirm (display) offset type LTFT. For both banks it was 0.00; for the second bank still – decreased multiplicative LTFT (comparing to first bank and values, which these LTFT had a day before):
Checking Rough run data was detected, that cylinder No.6 (No.4 according to firing order) has remaining increased mechanical efficiency both in the Homogeneous mixture and Stratified charge modes:
Checking Lambda control in Homogeneous mixture mode with help of NOx sensor, we have to make conclusions, that the average mixture actually is enriched:
Obviously, the fuel mixture between cylinders is balanced very incorrectly. Additional confirmation for it – MSD80 is not able to correctly install the reference point for control probe of the 2nd bank:
Increased voltage of the control probe confirms – MSD80 is not able to calibrate the wideband probe and/or is not able to equate fuel mixture between cylinders (in this situation – the average fuel mixture of all bank is enriched).
Checking ../F5/Shift + F6/F5, we see, that the idle compensation of the cylinder No.6 in Stratified charge is inadequate – the opening time of the injector is significantly decreased:
Viewing live data of the injectors (the engine runs in Stratified charge) ../F5/Shift + F6/F1, we get confirmation, that the injector cylinder No.6 really is opened for much more shorter time:
Two times shorter opening time, but, comparing to other cylinders – increased mechanical efficiency? It is NOT normal!
In the same time – no error messages in the MSD80 error message memory.
Correction of the injector cylinder No.6 in Stratified charge after a while, in idle, overreached allowed values:
In turn, opening times in Homogeneous mixture showed, that the individual corrections for cylinders are already turned off:
As a confirmation for it – with these, practically the same opening time data for injectors, rough run data shows inadequate situation:
And still – no error messages in MSD80 memory, the even persistent vibration of the engine in idle can be felt, and Rough run data confirm it.
After a moment – the engine starts to work in Mapped mode. Not taking into account the oil temperature 100 oC, the engine temperature was decreased to exactly 80 oC. And still – no error messages in the MSD80 memory!
It is clear, that the cause of the problem is injector of the cylinder No.6, which, when driving longer distances (and when the engine/injector heats up), don’t close in time or is leaking significantly. I’m amazed at MSD80 reaction – not taking into account, that:
a) from the beginning of the adaptations they are not able to even the performance of the cylinders in the Homogeneous mixture (confirmation of it – turned-off individual offset correction of cylinders with persistent mechanical disbalance);
b) MSD80 don’t confirm the creation of offset type LTFT (obviously, because of inability to finish an evening of the fuel mixture in cylinders);
c) also tests of mechanical efficiency, performed in Stratified charge mode, idle, confirm abnormal required correction for cylinder No.6 (more than -2.8 mg/stk, which usually initiates error message regarding trim control, cylinder X).
No error messages were recorded in MSD80 error message memory!
The story of this entry allows to make several conclusions:
a) if MSD80 is not able to finish the evening of the cylinder efficiency in any of the performance mode, it turns off this functionality completely (not, for example, tries to perform max possible correction);
b) if necessary correction for any of the injectors go out of the allowed corridor, there can be situations, when error messages regarding fuel trim, cylinder X, are not recorded in the error message memory within a reasonable time (for example, during 5 .. 10 min) (obviously, to confirm the error message several conditions are required: either n number of tests, which confirm exact problem, or confirmation of the problem in several driving sessions or driving conditions);
c) the engine can start to use also other emergency modes, even without recording the error messages – this time it was Mapped mode.
We should thank-you the INPA, which gives the most amount or necessary basic information – the cause of the problem is clearly visible. But what can specialists of the dealer centers to do – they are not allowed to use INPA, as we know? Obviously, only powerlessly confirm – yes, the engine vibrates, no error messages are present. Also, the creation of new adaptations doesn’t help.
After making the decision (the injector of cylinder No.6 was declared as damaged), the injector was replaced, then it was coded, all fuel adaptations were deleted, new adaptations of flywheel and fuel were created.
After creating new adaptations, MSD80 correctly confirms:
a) offset LTFT +0.7/+0.8 mg/stk for both banks;
b) multiplicative LTFT +16/+20 % for both banks;
c) Stratified charge, idle mode applied around +0.5 mg/stk for cylinder No.6;
d) Rough run data shows a correct mechanical balance between cylinders, vibration in idle was gone both for Homogeneous and Stratified charge modes.
After several driving sessions.
As we see, both offset and multiplicative LTFT are correct for both banks:
Voltages for both control probes – correct:
NOx sensor confirms correct average Lambda value:
Injector correction data in Stratified charge, idle:
Rough run data are correct – they change “polarity” regularly:
Of course – the normal thermal mode of the engine is restored, including Eco mode:
Misfire counters after 2 hours driving session: