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The mixture
correction is carried out at idle / partial load via the O2 BLM CELL CONT if
the integrator deviates from the ideal (stochiometric) air-/fuel ratio over a
longer period, and the full-load enrichment is ACTIVE.
The cell
number given in test step 21 (O2 BLM CELL CONT NO.) decides whether the
modification (mixture correction) is carried out in the idle speed memory
range or partial load memory range. As the control units have been programmed
differently, it is impossible to indicate the exact borders or transmission
points between the various O2 BLM CELL CONT NO. cell numbers. In the event of
the O2 BLM CELL CONT NO. 18 or 19 not being attained, with the engine at idle
speed and at operating temperature, first check whether the engine is really
at idle speed or in another load status (e.g. due to an air leak or if the AC
is switched on).
If the
value in test step 21 is not within the permissible limits for longer periods
and the control unit or engine is OK, then this test step does not have to be
further considered. If, however, there is a complaint or the engine is not
running properly, replace the control unit after thoroughly checking that
there are no air leaks or other possible damage.
The purpose
of the O2 BLM CELL CONT is:
to increase
the value (if the mixture is too lean and therefore the integrator greater
than 128) until the integrator is on average 128 again.
or: to decrease the value (if the mixture is too rich and therefore
the integrator less than 128) until the integrator is on average 128 again.
The O2 BLM
CELL CONT value is a tolerance for components, it also reacts however to
influences such as engine friction, air leaks etc.
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