BMW has completely reworked the algorithm of maintaining the idle of the MSD87/F series in Homogeneous mode. Also, the information, which is available for these DME, is different (both in INPA and ISTA D/+). It is logical, that also the most efficient way, how to identify leaking injectors during cold start, is different.
Leaking of piezo injectors during the cold start is one of the most popular problems. When cold weather starts, in the moment of the start the vibration of the engine appears, the smell of unburned fuel can be felt from the exhaust.
Recommended diagnostics tool: INPA for F series, N54 loader 3.700
Critical minimum: ISTA D/+
Additionally required: EML 327 adapter
With what to start?
First critical condition: the engine (when it is warmed up) has to use a Stratified charge. So: the NOx system has to be in work order.
Reason: when the engine works in a Stratified charge (and only in this mode), DME can measure several important parameters of the injectors: leaking in the closed condition, reaction time, quality of fuel atomization, etc. These measurements are necessary for the creation and update of the adaptation maps of injectors. If the engine does not use a Stratified charge, these measurements of the injectors are not possible, their adaptation maps are not updated. With outdated injector data DME:
- for the cold engine – will use completely incorrect reference data of each injector and will not be able to compensate differences of the parameters – there will be the vibration of the engine, misfires;
- you will make wrong decisions when identifying damaged injectors.
Before to start preventing the problems with the cold start of the engine:
- evaluate if the engine uses Stratified charge, description here;
- if the engine does not uses Stratified charge, restore the usage of it;
- perform quality re-adaptation (at least 200 .. 300km, several driving sessions, several cold starts).
It is possible that after restoring the Stratified charge and re-adapting the engine, the problem will disappear. But, if the Stratified charge is restored, the re-adaptation is performed, but during cold start still, the unevenness of the engine, vibrations appear – continue the diagnostics.
1. Start cold engine. Evaluate its performance during the first 10 .. 20 seconds (while wideband Lambda probes have not started to work).
Possible scenarios:
- the engine works with all 6 cylinders;
- the engine works with all 6 cylinders, but time after time shivering can be felt (some cylinder is misfiring);
- the engine vibrates strongly (obviously, at least 1 of cylinders is not working).
If you have difficulties to indicate if all cylinders are working (it is possible in a situation when/if your experience is little), before starting the engine:
2a. if you will use ISTA D/+: open Operational smoothness values
Note: in this menu, the cylinders are marked in placement order, positive value – reduced mechanical efficiency of the cylinder.
2b. if you use INPA, open Rough run menu ../F5/F7
Note: in this menu, cylinders are numbered in the firing order (1/5/3/6/2/4); positive value – reduced mechanical efficiency of cylinders.
3. Start the engine, evaluate the mechanical efficiency of cylinders. If Rough run of any cylinder indicates large positive values (+5 .. 7 units): the cylinder is not working.
If some cylinder is not working, the cause is:
- strongly leaking injector;
- problems with ignition (ignition coil, spark plug).
Check the spark plugs, if necessary – replace them. Replace the ignition coil with the neighbor cylinder. If the new spark plug is getting flooded again, replace the injector with the one from a neighbor cylinder or replace the injector with a new one.
The task in this stage of diagnostics – to get all cylinders working in the first 10 .. 20 seconds after start.
4. After 10 .. 20 seconds the wideband probes will be warmed up and will start to work. Evaluate Lambda in both banks.
4a. If you use ISTA D/+, choose: Signal, oxygen sensor before catalytic converter, Bank1 un Bank2 live data
4b. If you use INPA, pay attention to indications of the voltage of Lambda probes in Rough run menu
5. If the Lambda voltage of any bank is below 1.98V, it means: Lambda < 0.99 (the mixture is rich). Obviously, some injector of this bank is leaking so strongly that DME is not able to provide correct fuel mixture not in individual cylinders, not in bank overall. In the future pay attention exactly to the 3 cylinders of this bank.
Note: in this stage (when Lambda probes are warmed up an are adjusting the fuel mixture) differences of mechanical efficiency of cylinders and vibration of the engine can appear.
6. If the voltage of Lambda probes of both banks is around 2.00V, it means: DME has successfully stabilized the correct fuel mixture in the range of the current bank. In this situation – evaluate the mechanical efficiency of cylinders in the range of current bank:
6a. if you are using ISTA D/+: a group of cylinders 1;2;3 and 4;5;6;
6b. if you are using INPA: cylinders on the “left side” (1;3;5 by firing: first bank) and the “right side” (2;4;6 by firing: the second bank).
7. If the mechanical efficiency of all three cylinders of the bank is similar (different from each other by -0.300 .. +0.300), at this moment DME has succeeded in even the mechanical efficiency of cylinders. If the mechanical efficiency of some cylinder is increased (its indications are below -0.300 against other 2 cylinders of the same bank) – DME has not managed to even the mechanical efficiency of this cylinder. Reason: The injector of this cylinder is leaking.
Example:
In each bank, you see the cylinder which indications are significant “more negative” than for other cylinders of this bank:
- 1/1 (by firing order/placement) in the “left side” of the 1-st bank;
- 2/5 (by firing order/placement) on the “right side” of the 2-nd bank.
Conclusion: injectors of cylinders No.1 and No.5 (by placement) has to be replaced.
Note: after replacement of the injectors they have to be encoded, re-adaptation has to be performed.
8. If the engine still shivers time by time, use EML 327 adapter to evaluate Misfire counters. Solve problems with a cylinder, which has an increased number of misfires in the actual session. More exact info, how to use misfire counters, read here.
In especially “hard” cases, several injectors in the same bank can be leaking, so the previously mentioned actions will have to be repeated for several times till all culprits will be found.
After this stage, the following result should be achieved – during cold start:
- the engine starts with all cylinders, no permanent vibration and/or shivering (misfires) can be felt;
- Lambda probes indicate correct Lambda (Lambda = 1.00 or indication of the probe: 1.99 .. 2.01V) in both banks;
- mechanical efficiency of all cylinders is similar, fits in -0.300 .. +0.300 and after some time (1 .. 5 seconds) change “polarity”.
If you have INPA, you can perform additional “health” checks of the injectors. Previous tests ensure, that in current conditions DME has managed to stabilize the work of all cylinders. But these tests doe not give a notion, how “hard” DME had to work to reach this optimal situation. It could be, that after repair (and replacement of leaking injectors), all injectors work perfectly. But it could also be that some injector is still leaking. At this moment DME has managed to compensate its leaking completely, but – if tomorrow it will be already 5 .. 10oC colder? The engine will vibrate again!
Unfortunately in ISTA D/+, no data of injector corrections are available, so how you have to use INPA.
9. Open ../F5/F9
Note. In this menu:
DFT coefficients – parameters, which characterize the difference between the ideal and real performance. The smaller the values, the more stable and more correspondent the situation to the required torque.
The upper value of each cylinder – correction, applied to the injector;
The lower value of each cylinder – mechanical efficiency of each cylinder (increased value: increased efficiency);
This algorithm works till 1500 RPM, also when driving (not only in idle)!
Evaluate corrections, applied to each injector, and compare it to other cylinders. If data of correction of any injector are significantly different from others – obviously, its parameters are “floating” or its parameter difference from normal is increased (DME has applied max values in its adaptation map).
Note: this menu can be used also while driving, observing the “health” of injectors by different openings (low, average, high required torque). Such a driving session allows noticing also mores specific defects (for example, bad atomization in different driving conditions).
