Method for detecting coking in the inlet section of an internal combustion engine with a variable inlet valve lift controller

A computer product comprising a non-transitory computer readable medium having stored thereon program code which, when executed on a processor, carries out the acts of:

• ascertaining a correction value which is offset as an offset value against a preset valve lift by the inlet valve lift controller;
• carrying out a first quantity deviation test by way of which a first air ratio value is ascertained which is formed from a lambda value measured during the first quantity deviation test and a desired lambda value of a fuel combustion in combustion chambers of the internal combustion engine, wherein, in the first quantity deviation test, load control is performed by way of the variable inlet valve lift controller;
• carrying out a second quantity deviation test by way of which a second air ratio value is ascertained which is formed from a lambda value measured during the second quantity deviation test and a desired lambda value of the fuel combustion in the combustion chambers of the internal combustion engine, wherein, in the second quantity deviation test, load control is performed by way of the throttle flap;
• determining a comparison result from the first air ratio value and the second air ratio value;
• and
• determining whether coking is present in the inlet section of the internal combustion engine by combined evaluation of the comparison result and the correction value.

An apparatus, comprising:

• an engine test unit that detects faults in an inlet section of an internal combustion engine, wherein the engine test unit is operatively configured to:
• ascertain a correction value which is offset as an offset value against a preset valve lift by the inlet valve lift controller;
• carry out a first quantity deviation test by way of which a first air ratio value is ascertained which is formed from a lambda value measured during the first quantity deviation test and a desired lambda value of a fuel combustion in combustion chambers of the internal combustion engine, wherein, in the first quantity deviation test, load control is performed by way of the variable inlet valve lift controller;
• carry out a second quantity deviation test by way of which a second air ratio value is ascertained which is formed from a lambda value measured during the second quantity deviation test and a desired lambda value of the fuel combustion in the combustion chambers of the internal combustion engine, wherein, in the second quantity deviation test, load control is performed by way of the throttle flap;
• determine a comparison result from the first air ratio value and the second air ratio value;
• and
• determine whether coking is present in the inlet section of the internal combustion engine by combined evaluation of the comparison result and the correction value.