Hi,

this graphic shows the firing order of the M113:



Source: OLDTIMER: Tipps für Mercedes Geländewagen 460/461/463 und 230 460 und 463

There are also other aspects concerning ignition:

For the following operations, a firing angle adjustment is done:

Catalyst heating, idle, fuel cut-off, transmission overload protection, ESP / ASR control operation, smoothness evaluation, knocking tendency, anti-knock control.

Catalyst heating: if the coolant temperature is between -10 and +40 degrees Celsius, in addition to the increased idle speed, the ignition angle for about 20 seconds are set in retarded ignition.

Idle: For faster control is not adjusted by the throttle, but the firing angle is changed.

Fuel cut-off: a torque shock is prevented after the injection valves actuated again, by moving ignition momentarily to "late".

Transmission overload protection: During the switching process (1-2, 2-1) is the ignition is momentarily moved to "late" - this reduces the engine torque.

ESP / ASR control operation: if the angle of the throttle is reduced wihile ESP/ASR is activate, the ignition is momentarily adjusted to "late" .

Smoothness evaluation with two knock sensors: Combustion misfires - the catalysts must be protected against thermal overload - to to this the injectors are no longer actuated.

Knocking tendency: At elevated charge air (> 35 degrees Celsius) and coolant temperature ( > 100 degrees Celsius ), the ignition angle adjusted to "late " to reduce the tendency to knock.

So there's a lot more stuff going on.

Regards
Markus