Today’s patient: F12, 650i with N63 series petrol engine. Beautiful and well-equipped cabriolet, the poshest model of BMW, till the new 8-th series was presented.
The exact vehicle has “visited” a local dealer with complaints regarding the uneven performance (shivering) of the engine. Under warranty, the repairs of around EUR 4500 .. 5000 (as if) were done, the dealer didn’t manage to solve the problem. The car is in the same pitiful condition as it was before the visit to the dealer center. The car is returned to the customer.

When the engine is started, it shivers even when it’s warmed up. Even in idle. After a few seconds, some cylinder switches off. The shivering is so strong, that it even makes no sense to do a test drive to look for a problem – the problem can be felt very well. The car is not usable.

Let’s see, what does ISTA (the diagnostics tool, which is available to the dealer) show. Here, the problem with the cooling of the turbochargers.

Notice: to solve the problem with the overheating of the turbochargers, they are colled both with oil and cooling agent. For the cooling agent the pump, which is managed via LIN serial interface, is intended. Here, there are problems with this pump (in some moment it has indicated very low current consumption – there could be troubles both in the cooling contour or the pump itself). Yes, when we did a visual inspection of the pump, we indicated, that someone has hit it – obviously, someone has attempted to “repair” it in such a way. When it turned out, that this “method” was not working, the repair “specialists” haven’t been able to figure out other techniques.

Yes, the hitting definitely would solve all problems of the electronically manageable motor! We will return tor this problem later.


Do we see anything regarding the shivering of the engine? Yes, we do! Here, the problems are in 2-nd and 7-th cylinders.

And – there are problems in other cylinders too!

When choosing the Repair plan, this problem is marked with a high priority, named as “Misfiring detection”, and ISTA offers repair activities. It is clear, that misfiring usually is caused by problems of the ignition, the dealer is asked to replace the spark plugs and ignition coils. As if simple, isn’t it? But – let’s check the situation more seriously. Let’s see, if the dealer has followed to the directions of ISTA and performed the repair.


In the next step, we will use the equipment, which is not available for the dealer – ELM327 adapter.
Note: for this DME, the “Misfire counters”, which can be seen also by ISTA, are available for the dealer. Yes, only one counter for each cylinder, but the data ARE available! Of course, you still have to know, how to use this data…

Here, what the misfire counters say. The following screenshot was done after the idle session of approximately 5 minutes.

As you see, there are serious problems with misfire for at least 3 (!) cylinders! Incorrect fuel mixture?


ISTA live data indicate the following picture:
the voltage of the wideband probes in both banks: 1.98 .. 2.02V;
Lambda in both banks: 0.99 .. 1.01;
the voltage of the control probes: 0.70 .. 0.80V;
adaptations in both banks – confirmed and correct.
The conclusion: the (average; entire bank) fuel mixture is correct!

Incorrect fuel mixture between cylinders due to VVT problems? Let’s open Rough run data.
Mechanical efficiency of all cylinders -0.02 .. +0.02ms. So – the fuel mixture of each cylinder is also correct!

Correct fuel mixture, but continuous misfires? My experience says – the repair has to be started with a check-up of the spark plugs. There is a very small possibility, that mass “infection” of the ignition coils could be started.


Let’s start with cylinder No.8.

We can see, that the spark plug has already served for a quite long time. Its air gap has burned quite wider than for a new spark plug. Another weird thing – the OEM spark plug has a different temperature class, its dielectric is noticeably longer than the one for a spark plug, used before.

Counterfeit? Who knows…

Here, for example, the spark plug of cylinder No.7. I should say, that something like that I see for the first time in my life – I truly wonder, how this spark plug was still able to work!

Here, the spark plug of cylinder No.2. Complete nightmare!

The spark plug of cylinder No.5 doesn’t look much better…

At this moment I have a question – what kind of “repair” did the dealer service performed? It is clear – the spark plugs haven’t been even inspected!
I remember the reply of the head of the dealer service to my question, how often the spark plugs of the BMW engine should be replaced: “they don’t have to be replaced at all”. When I asked once again to make sure, if didn’t misunderstand, he specified: “well, you have to replace them if the engine shivers strongly…” Gentlemen, this is the case, when the engine SHIVERS, and you haven’t even INSPECTED the spark plugs???

But there is even more interesting case with the ignition coils. In all cylinders, except No.2, the ignitions coils, manufactured by Bosch, are installed. Formally, for this exact car, the ignitions coils of Bosch are not even listed, but such ones are listed for older vehicles with N63 engine. I have no objections to Bosch – they are really high-quality ignition coils.
In the cylinder No.2, the ignition coil manufactured by Eldor is installed. Eldor has replaced Delphi during the last few years, so – this ignition coil has been replaced relatively recently. Obviously, the “repair” of dealer service was limited by the replacement of the ignition coil of cylinder No.2. Most probably – the ignition coil was replaced and… There were no improvements. Yes, the “clogged” spark plug could be one to blame. But there is one more reason, why this attempt of the dealer failed.

The firing order of N63 series engine: 1/5/4/8/6/3/7/2
Do you see anything suspicious? The cylinders No.2 and No.7 are sequential. In the moment of a misfire, the flywheel “frowns” a bit and “shivers” due to inertia – DME needs a serious “effort” to understand, what caused this uneven performance. If the engine has serious problems with cylinder No.7, DME sometimes can falsely identify also the next cylinder (by firing order) as misfiring one.
If the dealer would have been replaced the spark plugs and the ignition coils in both cylinders, indicated by ISTA, it is possible that the problems would be highly lessened (of course, by condition, that the misfires are caused by the problem of the ignition coil). Unfortunately, the experiment with the spark plug of cylinder No.2 was doomed to failure. Unfortunately, the cylinder No.7 continued to misfire, and DME continued to identify the cylinder No.2 as damaged.


At the first stage of repair, the spark plugs were replaced. Here, the situation after driving session of 10 minutes:

As you see, the cylinder No.7 dominates strongly. Problems of cylinder No.2 – much more less. DME has identified the “worst” cylinder in each bank, unfortunately, this aspect deceived the “specialist” of the dealer center so much, that they declared this car as unrepairable.


Next stage: replacement of the ignition coil of cylinder No.7.
After replacing the ignition coil, we have to conclude that the problem in cylinder No.7 unfortunately still exists. Here, data after driving session of several minutes:

In the actual session: cylinder No.7 has 50 misfiring events, other cylinders – only several. It is remarkable, that cylinder No.2 has 0(!) events.

It is interesting, that after replacement of the spark plug, the cylinder No.7 in idle runs very correctly, accordingly – the mechanical problems of the engine are unlikely. The next step – swap the injector with the injector or neighboring cylinder to be 100% sure, that the problems with the injector are real and to avoid unnecessary spendings.

And more – not taking into account, that in last driving sessions the misfire events in cylinder No.2 were 0 (cylinder was working perfectly), DME stubbornly continued to record the error messages also regarding this cylinder. Obviously, these DME use long-term (between sessions) misfire counters to record the error messages. It has to be taken into account – so: to evaluate the truthfulness of the misfiring error messages, the longterm counters (at least – using Start/Stop button) have to be cleared. Otherwise, it can happen to fight with fake error messages.


For a little rest from misfire problems. When performing the inspection of the car, my colleague listened the sound of the secondary pump of the contour (conclusion – the pump works!) and decided to check, it the “dry run”, mentioned in the description of the error message, could be true. Here, the image of the expansion vessel of this contour:

there is NO cooling agent in the contour! So – the dealer has not checked the levels of the technological liquids (and has not added them, if necessary), but also haven’t reacted to the “dry run” error message! We can assume, that the technical personnel has problems with basic knowledge of English, but ISTA is available also in Russian. Or – a “true specialists” do not know any language?


Returning to the theme of misfires – after replacing the spark plug and ignition coil, cylinder No.7 still experiences misfire problems. Obviously, the injector injects fuel incorrectly. The amount of injected fuel corresponds to required, but we can assume, the fuel is injected in an incorrect angle and floods the spark plug.
It was decided to swap by places the injectors of cylinders No.8 and No.7, to get a 100% confirmation, that the injector is one to blame.
After driving session of 2 minutes (after swapping the injectors):

Here, the actual session:

  • cylinder No.7 – 4 misfire events;
  • cylinder No.8 – 80 misfire events.

The problem has traveled from cylinder No.7 to cylinder No.8. We got a 100% confirmation, that the ex-injector of cylinder No.7 is damaged. Solution – replacement of the injector.
And then – encoding of all injectors, re-adapting of the engine. Why all injectors have to be encoded? Because it turned out, that they are not encoded. Yes, I understand, that the injectors were replaced earlier (obviously, another dealer service, because the vehicle had a warranty, most probably it was performed in the “homeland” USA), but – the local dealer has neither detected nor solved this problem…


At the end of entry – several notes:
1. all mentioned repair steps: checking and replacing of the spark plugs, replacement or swapping between neighbor cylinders of the ignition coils, finally – swapping of the injectors between cylinders, is described in the ISTA Repair plan. This is the obligation of the dealer to follow the instructions. Yes, the dealer has sligh problems with readings of the misfire counters, but if the dealer would have followed the directions of ISTA and worked with cylinders No.2 and No.7, the car would be repaired (the customer, thou, would overpay for replacement of injector of cylinder No.2);
2. is not that the misfire counters for these engines are not available. The total misfire counters can be read by ISTA. To use them:

  • write down the existing counters;
  • perform driving session;
  • read new values of the counters, calculate the delta.

3. In newer versions of ISTA+, Expert mode, after test block of cleaning of the spark plugs, ISTA offers logs and graphics of the misfiring data. Here I have to mention, that the analysis of these data is done completely useless, graphics – maximally incomprehensible, but – if you try hard, the guilty (the one, who has troubles with misfires) can be found. Yes, the complete evaluation of this test block is: FAIL, but the block is itself earns a separate blog entry.

And finally, I want to add – this is not the first entry regarding the unprofessional performance or even such an action, which is even limited to fraud, of the dealer service or certified dealer center. But this case is unique with – the dealer is not even able to check the levels of the technical fluids, not even talking about refilling them. The dealer service doesn’t even understand the basic correlation of problems and does not perform the initial works of the maintenance (for example, replacement of the spark plugs).


p.s. situation after replacement of damaged injector:

As we see, all problems are gone – just 1 misfire event is detected for 8th cylinder. Now 6th cylinder dominates – it will receive a brand new ignition coil!