Problem with W204 RPM Fluctuations

[LLBG]

For your problem with RPM fluctuations and lambda - check the wiring. As you know, MB has some problems with wiring installation. You can replace many modules, but if the wiring is not ok...

 

[B0bby92]

Could you please elaborate on how to check the wiring? And is it possible to replace it?

 

[dewidhaselhof]

I had exactly the same problem with my C180 Kompressor, it was caused by a clogged catalytic converter.

 

[LLBG]

You can do it yourself. All wiring harnesses from sensors to ECU should be checked for abrasion/wear/breaks. If they have wear-resistant insulation, then even if you test them with a device, they will mislead you. The problem is that the insulation is damaged and there is interference when the car is moving.

 

[B0bby92]

I had exactly the same problem with my C180 Kompressor, it was caused by a clogged catalytic converter.

As far as I know, the catalytic converter on the C220 diesel with the OM646 engine does not have any clogging issues because it is followed by a DPF. I removed the DPF.

 

[LLBG]

There is a big difference between diesel and petrol engines and how both systems work. I am almost certain it is an electrical problem!

 

[Greed]

The DPF cannot guarantee the correct functioning of the catalytic converter. Its efficiency largely depends on the quality of the fuel.

 

[B0bby92]

There is a big difference between diesel and petrol engines and how both systems work. I am almost certain it is an electrical problem!

Any suggestions on what I should check in the electrical system?

 

[kaurisalkdasjds]

All this is trial and error, you can check it with a multimeter, connect one pin to the engine ECU connector and the other to the other end to measure the cable break. You can also visually check, a slight compression of the cable can be the cause of the break or measure the values of 2 pins, for example, the lambda probe heater circuit and compare the values.

 

[LLBG]

It's not that simple. When the cables from the car modules and ECU are disconnected, everything looks normal on the multimeter, but when the engine is running, the problems remain.