N53. Problem of cylinder No.3

Manifestations of defect – uneven running of the engine, misfires.

Checking error message memory, very often you will find error messages regarding fuel trim of bank No.1, CO catalytic converters of bank No.1 and/or trim of Lambda probes (together with misfires in cylinder No.3 , or even No.1 and No.2).

The cause of problem – oil getting onto “neck” of ignition coil for cylinder No.3 and also on insulator of spark plug.

When the oil is refilled, quite often small or not even so small amount of oil gets onto decorative cover of engine.

During time, valve cover gasket (10) looses it’s flexibility, also the decorative cover experiences deformations. And very often (due to regular need to take off the decorative cover) it is fixed only using two screws at front – this obstacle increases the problem.

Thru the opening in cover (11) the oil seeps along the valve cover gasket (10) and gets on the body of ignition coil or cylinders head of cylinder No.3 and then leeks to “neck” of the ignition coil. There is no accurate information, how significant is the impact of clean (fresh) oil, but in BMW after-sales materials it’s underlined, that, for example, fuel damages insulation properties of silicone “neck”, and its categorically forbidden for fuel to get on the ignition coil. Moreover, the leaked oil contributes to dirt getting on ignition coil and spark plug – the dirt for sure is not a good insulator!

In any case the oil have been leaking along the valve cover gasket (10), after some time the ignition coil of cylinder No.3 look’s like this (see the pictures).

Areas marked with red are the one on ignition coil, to which attention has to be paid:

1. elongated, dark grey lines for Bosch ignition coils – if they are very clearly visible: the coil has to be replaced (in this place high voltage breaks the insulation);

2. brown, burned areas – oil has gotten on the “neck” and burned on;

3. end of the “neck” – there also oil residue is visible, inside of channel with light lines – the high voltage has “traveled” around the spark plug.

Significantly, that not always the cylinder No.3 is marked as the “guilty one”, when the error messages are recorded. Sometimes the cylinders No. 1 and 2 are marked (and also really are) as misfire. The reason of such situation is very simple: if cylinder No.3 misfires not often enough to record the error message regarding current cylinder’ s damage, MSD80 (due to faulty algorithm) detects large unevenness of running (decreased average efficiency of cylinder no.3) increases the average fuel amount in it. As a result – to keep correct fuel mixture for whole 1-st bank, the fuel mixture in cylinder No.3 is enriched, in cylinders No.1 and 2 – lean. Cylinders No.1 and 2 start to misfire, and the MSD80 registers it as error messages. Of course, there is no result when changing plugs, ignition coils and even injectors in cylinders No.1 and 2 – an one more “not repairable” N53 is here!

Note: in situation described, the error message memory is also supplemented error messages regarding fuel trims in bank No.1, insufficient performance of CO catalytic converter for bank No.1, trim problems of Lambda probes for bank No.1. Of course, none of the components is been damaged – the problem with ignition coil for cylinder No.3 has to be solved, and the adaptations of the engine has to be performed repeatedly.

Attention: also the insulator of spark plug has to be clean! The spark plug has to be taken out, the insulator and also the tool used for screwing out the spark plug has to be cleaned. The shaft of spar plug has be cleaned also! The valve cover gasket has to be checked for leakage; if one is detected – the gasket has to be replaced immediately!