In this entry: step-by-step recommendations for restoring the performance of the N53 engine.

Available diagnostics tool: INPA for F series. N54 loader 3.700

Symptoms: increased fuel consumption, permanent vibration, uneven performance, low-quality idle.



1. The manufacturer of the car has decided to hide the information regarding its problems from the users (also diagnostics specialists), so a range of parameters has to be investigated, using live data.

2. In this entry, the following case is described: no error messages in the DME error message memory (or there is a 12C401 error message and the NOXEM is installed), but the performance of the engine is unsatisfactory. In situations, when the error messages are recorded in the DME error message memory, use the option “Calculated test plan” of ISTA D/+ and prevent the obvious problems at the first hand.

3. In addition to the INPA tool, you will need also ELM 327 adapter with the required software to read the Misfire counters, which are reported only in OBD Mode 6 (and are not available in INPA; ISTA D/+).


Stage 1. Restoring the Stratified charge


Make sure, if the engine uses a Stratified charge. If a Stratified charge by some reason is not used, all symptoms, mentioned at the beginning of this entry, will be typical for the performance of the engine – the engine works in an emergency mode. To make sure that the engine uses a Stratified charge, follow here.

If the engine uses a Stratified charge stable (for a longer period of time, a positive result confirmed during several following driving sessions), move to the next tests.

If the engine does not use a Stratified charge, at first the use of it should be restored. How to restore a Stratified charge?

a) the most typical reason why the Stratified charge is not used: contamination of the NOx catalytic converter is above the norm. Unfortunately the F series vehicles do not record any error messages in DME in this situation (there are no appropriate error messages intended for F series!). To solve this problem, perform the desulfation session of the NOx catalytic converter as described here.

If the desulfation session is successful, check the usage of the Stratified charge after desulfation session, driving with speed 60 .. 90km/h.

If the desulfation session is unsuccessful and even increased driving speed (till 140km/h) does not help to activate it, you have to make sure, does the NOx system works at all.

Disconnect the NOx sensor for a moment, start the engine. The following error message should appear immediately: ”CD8510: Lost communication”. If this error message does not appear – obviously, the DME software has been “upgraded”: some “benefactor” has tuned off the NOx system. In this case – at first, the stock software has to be restored.

If the error message regarding the NOx system appears, we can assume, that the software is correct. In this case, try to increase the driving speed to 140km/h and maintain it for several minutes to start the desulfation session. Don’t forget to fill the fuel – the fuel tank has to be full for at least 50%. If also this does not help, it is very possible, that the OEM NOx sensor has a hidden defect (more info here). If you wish, you can send the NOx sensor to us for the check-up (more info here).

  • If the desulfation session is not successful, or;
  • the Stratified charge is not restored after successful desulfation session, or;
  • due to different reasons, you can not drive with increased speed:

b) delete the adaptations of the engine and create new ones, as described here. Deleting of adaptations, using INPA, will exclude a range of possible hidden problems from the list of possible problems: insufficient performance of CO catalytic converters, the uneven performance of the engine, incorrect injector adaptations, etc. and – will clear contamination of NOx converter (calculated mathematically). If the Stratified charge is restored – move to the next tests. If the stratified charge is not restored or turns off after a short moment is can not be restored again (and the car has an OEM NOx sensor installed) – obviously, the sensor has a hidden defect and it has to be replaced.

Note. If the car has OEM NOx sensor installed and the performance of the NOx catalytic converter is lowered (the typical situation for these cars, taking into account, that they are more than 5 years old), Stratified charge can be forbidden already after 1000 .. 1500km (or even sooner) – as soon as the contamination of the NOx sensor reaches 500 .. 700mg. Solution for this situation:

  • often desulfation sessions of the NOx converter (after each 1000 .. 1200km at least);
  • replacement of the NOx catalytic converter;
  • installation of NOXEM.


Stage 2. Restoring even performance of the engine


c) if you have reached this step, obviously, a Stratified charge (at least for a moment – several motor hours) was restored. It’s good news. Drive as even as possible for several motor hours, allow the engine to create new adaptations of fuel & other systems. Evaluate the result. If the uneven performance (shivering) of the engine can be felt, continue checking with:

  • spark plugs. The spark plugs of these engines have to be replaced after each 20 .. 30.000km. Very important – only appropriate spark plugs of NGK have to be installed! More about the common problem regarding the spark plugs read here and here;
  • ignition coils. Unfortunately due to the constructive defect, the resource of the ignition coils is quite limited. Several ignition coils may need to be changed even after several tens of thousands of km. More about this problem read here. If you see that the ignition coils are oily, have black “lines” on them, their “pipes” are cracked – the ignition coil has to be replaced. Install Bosch or NGK ignition coils – they are more sturdy and will serve for a longer time than others;
  • if the spark plugs are in good technical condition (or replaced) and the ignition coils look perfect, evaluate Misfire counters.

d) evaluation of Misfire counters. You will need an ELM 327 adapter with the required software. How to use EML 327, read here.

At first, evaluate the mechanical efficiency of the cylinders to make sure that all injectors work more or less correct:

  • open INPA, ../F5/F7 menu;
  • evaluate Rough run data.

If Rough run data of all cylinders fit in a range of -0.500 .. +0.500 (except the moments, when the engine shivers), move to the inspection of the Misfire counters. If the indication of the mechanical efficiency of any cylinder is negative and reaches over 0.500: the injector of this cylinder leaks in idle and has to be replaced.

Allow the engine to run in idle and after some time (not turning off the engine) read the Misfire counters. An increased number of misfires will indicate the damaged cylinder.

Typical apportionment of the “guilty” components:

  • 90%: ignition coil;
  • 7%: spark plug;
  • 3%: injector.

Note. In this menu, the cylinders are displayed in firing order, it means: 1/5/3/6/2/4

To identify the damaged component, you can use a “swap” principle – swap the possible culprit with the next cylinder. If the problem “moves”, when the misfire counters are read repeatedly – the “guilty one” has been found!

In this stage, you have to reach even the performance of the engine in idle and when driving evenly.


Remember – after replacing the injectors (if it’s necessary) it has to be encoded, repeated re-adaptation of the engine has to be performed.

Note: in Stratified charge mode, the engine is more “whimsical”, it means, the misfires appear faster than in Homogeneous mode. The spark needs max power to ignite the fuel. Every tiniest damage of the ignition system or even slightly incorrect beam of the injector causes misfires. So, don’t be surprised, that when the engine switches to a Stratified charge, some cylinder starts to misfire. You can find the culprit, reading Misfire counters.

If increased vibration is observed directly for the cold engine:

  • start the cold engine, open Rough run menu, using INPA;
  • at the moment when the unevenness of the cylinders start (wideband Lambda probes start to work), observe the mechanical efficiency of cylinders. If the mechanical efficiency is strongly negative (more than -0.500), the injector of this cylinder leaks and has to be replaced.

Detailed information relating cold star issues read here.


As a result of the previously mentioned procedures, you should reach:

  • the engine regularly uses Stratified charge;
  • the performance of the engine is even – no short-term shivering (misfires), no permanent vibration (consequences of leaking injectors) are observed.

In more complicated problem cases, read Part 2.