Today’s case – quite complicated defect. Additionally, the diagnostics had to be done remotely – it’s always more complicated than when all parameters can be inspected in person. Good thing, that the owner of the vehicle has managed to prepare appropriate circumstances to perform the repair, he had all necessary tools and also experience in skills in car repair. In this case, the distance of several thousands of kilometers cannot even be felt. Yes, we spent several hours during two days to make sure, that exact component is one to blame – but the spent time still compensates saved amount of money.
Patient: N53B30. Symptoms: unexpectedly rough run appeared, the engine shivers. Checking the error message memory, following error messages were found:
- 29CE misfirings, cylinder 2
- 3070 cylinder same adjustment via irregular running cylinder 1
- 3072 cylinder same adjustment via irregular running cylinder 3
It is obvious, that whole 1st bank has a problem, but apparent (most possible) cause – cylinder No.2.
Checking fuel mixture during next start of the engine:
we can immediately see, than really – the first bank has serious problems:
- offset type LTFT strongly reduced/negative;
- integrator – additionally reduced fuel supply for several tenths of %;
- not taking in account it (both previous correction mechanisms), Lambda is below 1.00 (it means, the fuel mixture is still rich!).
Rouhg run data show, that cylinder No.2 (No.5 in the menu: by firing order) has 0 efficiency!
And yes, as you can see, the average fuel mixture in Bank No.1 still is rich (voltage is < 2.00 V)!
Checking live data of injectors, we have to conclude, that:
the injector of cylinder No.2 is completely turned off!
In this situation, Lambda has to be around 1.40 (because the air flows in in all three cylinders, but the fuel – in only two). So, one of the injectors of the first bank is leaking much more than initially suspected. It is interesting, that, for example, multiplicative type adaptations are similar for all injectors – no other indications regarding any problems.
Here, data of adaptations of injectors in idle, Stratified charge:
From these data, we can see, that the adaptations of the injector of the 1st cylinder are out of allowed range. Additionally, the most interesting is, that the efficiency of a cylinder has been decreased (not increased, as if the injector would be leaking)! To balance efficiency, it was not enough with +50 % increased the opening time of the injector! Or – the flowrate is normal (or even increased), but atomization – very, very poor?
One of the cheapest possible causes – the defect of ignition coils. Due to group misfires (which are caused by the defect of the ignition coils) the cylinder could be disconnected, and also it’s average mechanical efficiency could be strongly decreased in idle tests.
Replacing the ignition coils (switching the ignition coils of the 1st bank with cylinders of the 2nd bank) for cylinder No.2, nothing changed. After deleting the error message regarding misfiring, the error message was restored, the cylinder – disconnected again.
Spark plugs also were checked – they were in perfect condition (the spark plugs were replaced several thousand km before).
All injectors of the 1st bank were taken out as in the image (picture from the Internet):
No, none of them was leaking!
After a moment we have to conclude, that the engine now works only on 4 cylinders!
As we see, now already cylinder No.2 and No.3 is disconnected. Such a harsh reaction of MSD80 I saw for the first time. So – the defect is already in these two cylinders, and additionally – also the cylinder No.1 has inadequate performance in idle? Defects of several injectors, appeared at the same time? Don’t sound credible.
And then the error message regarding decreased rail pressure appeared:
Of course, the cause of the defect was not the damage of HPFP, but the unexpectedly high amount of consumed fuel, which resulted in decreased pressure, when the pump was working with “got used to” PWM of the valve.
Assuming, that in the current moment the worst situation is with cylinder No.2 (only regarding this cylinder the error message regarding misfires in Homogeneous mode is recorded), the only thing, which was left to – disconnect the plug of the injector of cylinder No.2. We had to make sure, that DME doesn’t give a faulty signal to open its injector (what can be the cause for all problems with fuel mixture).
Finally some positive changes, when starting the engine with the disconnected injector of cylinder No.2:
Finally, the Lambda of 1st bank is above 1.00 – the fuel mixture is not rich anymore. Even more – the mixture is close to optimal: 1.40. Still the fault of DME?
To check, if the as if “disconnected” injector of cylinder No.2 is not opened, I asked the owner of the car to check the voltage in the plug of the injector. Average voltage was only 80 .. 100 mV, which means – no, MSD80 did open the injector.
Connecting back the injector of cylinder No.2 and starting the engine – everything fine, Lambda around 1.35. Could it be possible, that after some of the cylinders of the 1st bank “fell” out the allowed range, MSD80 totally “went crazy”?
After deleting the error messages and re-adaptation of the engine, fuel mixture menu displayed the following values:
Lambda of the 1st bank around 1.00; the value of the integrator: correct!
Screenshot of video – Rough run data:
As we see, the efficiency of all cylinders is in the normal range, and what is important – efficiency of cylinder No.1 is slightly increased (so the problem with decreased efficiency, obviously, is gone).
It happens, that some micropart gets in the injector – the injector starts to leak for some time. It happens, that the injector “gets fit” after some time – the foreign object is injected out. Yes, in case of such defects the reaction of MSD80 can be quite inadequate, but still – this current reaction was something new for me, but I decided – if the defect will not repeat, we can assume that it’s a bug of the software.
But if the defect repeats (for example, when starting cold engine) – one of the injectors has an unpleasant hidden defect, which has to be found.
Here, the situation is perfect:
As we see, offset type LTFT of the 1st bank is around +0.66 mg/stk, Lambda, and integrator – with perfect values!
“I’m a bit pessimistic of this…” said the owner of the car – and he was right… It came out, that the conclusions of cylinder No.2 as faulty one was a mistake and disappearance of its defect – just coincidence!
Next morning came with an unpleasant surprise:
As we see, now the cylinder No.1 is “finished” (it’s been disconnected)!
And fuel mixture shows the following situation:
As we see, the old problem has returned: Lambda strongly below 1.00 (enriched mixture), not taking in the account -30 % integrator and strongly negative (still around 20 .. 30 %) offset LTFT.
And, logically, swirls of unburned fuel are coming off the exhaust pipe:
Now checking the adaptations of injectors, we have to conclude, that multiplicative type adaptations are the following:
- around 45 % for cylinder No.1;
- around 75 .. 85 % cylinder No.2 .. 6.
These data in combination with disconnected cylinder No.1 and detected in previous day inadequate flowrate of the injector of cylinder No.1 in Stratified charge, made a conclusion – actually the guilty element is the injector of cylinder No.1, which has a sporadic defect with different manifestations! Additionally, the defect can manifest both as increased efficiency in Homogeneous mode and decreased efficiency in Stratified charge, with very late closing during a longer opening. Obviously, the piezo element itself is defective – it has lost “power” and so the injector (in the meaning of time) reacts inadequately to the signal. Or – the DME is defective (control cascade of the injector, which in MSD80 is realized on discrete elements) or increased series resistance (problem with plugs or wires) – in series with the injector.
As the owner of the car didn’t have the oscilloscope, whith which he could quickly check the signal (directed to the injector), we used alternative methods.
To make sure, that the injector of cylinder No.1 was guilty all the time, not, for example, damage in the DME output cascades of the injectors or in wires to the injector, it was switched in places with injector of cylinder No.4 (this cylinder was chosen to make sure, that the problem “travels” to 2nd bank).
After switching the injectors od 1st and 4th cylinders:
As we see, the situation has changed radically:
- offset LTFT of the 1st bank now is positive (signs of leaking injectors are gone), but LTFT of the 2nd bank is strongly negative – it means, now the 2nd bank HAS signs of leaking injectors;
- integrator of 2nd bank comes close to -30 %, but Lambda is below 1.00 (the mixture is still rich).
It’s clear, that now the 2nd bank has serious problems with fuel leaking!
Rough run data looks following:
Here is a total chaos, but most important: 5th (2nd) and 6th (4th) cylinders of the 2nd bank (on the right side of the menu) have similar mechanical efficiency, but 4th (6th) cylinder – totally different.
Note: the cylinder numbering in the brackets is in firing order.
Here, how the Stratified charge looks, idle:
Here we can clearly see, that the injector of cylinder No.4 (actually – the suspected 1st cylinder) is leaking – to even the efficiency of this cylinder, the opening time of the injector has been decreased significantly (to half)!
But the most interesting part is, that misfiring problems are also in cylinder No.5:
5th cylinder as damaged is detected falsely. The cause is the following: as the “new” injector of cylinder No.4 is leaking, wideband Lambda probe sees enriched fuel mixture in all 2nd bank. To normalize the situation, opening times of all the injectors of the bank are proportionally decreased. Accordingly – the fuel mixture of cylinder No.4 becomes more adequate (less rich), but the fuel mixture in cylinder No.5 and 6 – lean, and misfires appear in these cylinders. I think, that if we would wait a bit longer, the error message regarding disturbances of the performance of cylinder No.6 also would be recorded (Rough run data indicated periodical misfires also in cylinder No.6).
After replacement, encoding of replaced injectors and re-adaptation of the engine:
A we see, all problems are gone! Lambda, integrators are correct for both banks, injectors test shows correct performance!
This topic is the good example, how the sporadic defect of one injector can “cast a shadow” to other injectors, HPFP and hide.
Regulations of BMW AG determine – if misfires or trim problems continue after replacing the ignition coil or spark plug:
- if misfires (or error messages regarding them) or trim problems are in one cylinder – replace the exact injector;
- if in two cylinders of one bank – replace all injectors of the exact bank;
- if in three cylinders – replace all injectors.
As we see, this is the case, when due to a defect of one injector the dealer center would replace all injectors. The bill for the customer – at least EUR 1500.
And, if they would see the error message regarding HPFP – most probably, it will be also replaced. Costs? At least plus EUR 1000.
Yes, detection and identification of such hidden and sporadic defects take more than 15 minutes, in the same time – correct diagnostics significantly reduces repair expenses.
Most often heard counter-argument, which I hear from dealer centers – “We don’t have time for science. Our duty is not to minimize the expenses of the customer but to repair the car”. In my opinion, quite inadequate arguments.
And more – yes, the dealer center would not found this defect. There are several reasons, why:
- dealer centers are not allowed to use INPA, accordingly – adaptation data of the injectors, adaptation data of Stratified charge/idle, data of tests of chemical efficiency – nothing of this would be available to the diagnostics specialist;
- regulations of BMW AG determine, for example – replace the suspected injector with the injector of neighbor cylinder: in this case that would not help to find the quilty injector.