F10/11. Repair of N53. INPA. Part 2

In this entry: how to act, if the engine has restored Stratified charge; larger problems are eliminated, but:

  • the Stratified charge is turned off periodically;
  • the engine sometimes runs unevenly.

If the shivering of the engine is observed or Lambda (checking Stratified charge) drops from 2 .. 3.5 to 1.4 .. 1.6 (and, even if the switching to Homogeneous lean does not help – switch from Homogeneous mode with Lambda 1.00), possible reasons are:

  • misfires (cause: ignition problems of an incorrect beam of the injector);
  • uneven road.

I believe the uneven road doesn’t need any further explanation.

If the uneven road is not one to blame, check Misfire counters after a long driving session. Allowed values (of the actual session) of each cylinder: till 10. If any of the cylinders is dominating strongly: solve problems with its misfires!

Next possible cause – problems of some injector.

If the engine has no significantly felt permanent vibration, it does not mean, that the injector works properly. But, if parameters of any injector are “floating”, DME regularly will remeasure this (and others) injector to restore its adaptation map for different modes.

It could be more complicated to find such defects because INPA gives limited information regarding the adaptation data of the injectors.

More popular situation: for cold and partly warmed up (warmed till temperature when Stratified charge is turned on) engine the parameters of some injector “float” strongly (the injector starts to leak in the closed position or closes with long retention).


How to notice such a defect?

  • open injector correction data in INPA ../F5/F9;
  • evaluate the mechanical efficiency of cylinders and corrections, applied to the injector.

The upper part of the data of each cylinder: applied correction for exact injector;

The bottom part of the data of each cylinder: mechanical efficiency of the cylinder (positive value: increased efficiency).

Evaluate, if some injector has a significantly different correction applied. If the correction of the injector is significantly different from others, obviously – the parameters of the injector have significantly changed since the moment when the adaptation maps were created/updated for the last time.

Injectors, which parameters are fluctuating strongly, have to be replaced. After replacement – the injector has to be encoded, the engine has to be re-adapted.

Note: MSD87 is able to measure the mechanical efficiency of cylinders till 1500RPM, accordingly – the corrections of the injectors you can evaluate also when driving, by different values of the required torque.


Fuel mixture problems in idle

One of the reasons, why DME can regularly perform measurements of the injectors, desperately trying to remeasure them, could be the problems to create the Offset adaptations of the banks:

  • open INPA fuel mixture menu ../F5/F6;
  • scroll the menu down, till you see the Offset adaptations (last line of the menu).

If these adaptations:

  • are 0.00 mg/stk: due to some reason (the description will follow) DME has not been able to create these adaptations and confirm them;
  • are strongly reduced (reached -1.50 mg/stk: minimal value), reason – leaking injectors;
  • are strongly increased (+1.50 mg/stk: maximal value), reason – air-tightness problems of the inlet manifold.

If DME has not succeeded to create Offset adaptations, check the leaking of the injectors and air-tightness problems. More info here.


Insufficient performance of the CO catalytic converters

If DME detects the reduced performance of the CO catalytic converters in Stratified charge mode, it turns off the Stratified charge in the current segment (engine load/driving speed – the amount of emitted exhaust) or even in all driving conditions. After a time (if the tests of CO catalytic converters in Homogeneous mode will indicate “subsistence minimum” of its efficiency), DME will restore the Stratified charge and will restart repeated measurements of the performance of the CO catalytic converters.

Also, the identification of this problem is not easy. You can perform the re-adaptation of the engine and evaluate the results of pass/fail tests of the CO catalytic converter, as indicated here. You can wait – if after some time (several thousand km) DME records the error messages regarding the performance of the CO catalytic converter – it’s not a good sign. Definitely – this problem is a reason for the turned-off Stratified charge.