[W126 Coupe] 89 560sec

[Robert Karl Stonjek]

> Cats were introduced in the UK in late 1990/91 on the w126 models.
> 
> However, legally, it is only post 92 cars which require cats - so they are 
> easily removed, legally.
> 
> 
> talbir
> 
> 

In Australia, Cats were mandatory on all new cars from 1987.  But in Hong Kong, which was part of the UK in 1987, the non-cat high power version was still sold, which is where my 560 came from.

Unfortunately, in trying to fix a performance problem, previous owner/s replaced the CIS-E, EZL and fuel distributor with parts meant for the Australian version.  The problem that caused all their problems, which was never discovered and repaired, was a faulty air temperature sensor.  I can understand how this would happen as the sensor is not listed in the schematic of the CIS-E as a sensor.

In fact it connects to the altitude sensor.  Between air temperature and air pressure you can easily calculate air density and so the necessary fuel mixture for optimum performance.  If any of the sensors go out of range then the CIS-E seems to have a curious counterintuitive response.  In the case of my car, it made the mixture progressively leaner with ever higher revs until low power and even missing (from fuel starvation) occurred.

Unfortunately, simply fixing the sensor does not help matters as the CIS-E currently in the car was set up for the CAT version of the 560, and my car has no cat nor oxygen sensor.  Disconnecting the EHA lets the car run nicely.  It starts OK without the 'choke', as long as you don't pump away at that throttle (service manual says 'don't press the throttle during starting' and 'up to 4s of cranking is normal for the 560').

Robert
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