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Mixture correction at idle speed / partial load is
carried out via the O2 BLM CELL CONT,
if the integrator deviates from the ideal (stochiometric) air / fuel
ratio for a longer period of time, and the full - load enrichment is ACTIVE.
The cell number given in test step 13 (O2 BLM CELL NO. ) decides
whether the modification (mixture correction) is to be 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 transition points between the various O2 BLM CELL NO. cell numbers.
In the event of O2 BLM CELL NO.
18 or 19 not being attained, with the engine at idle and at operating
temperature, first check whether the engine is really at idle 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 13 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 further 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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