Mercedes-Benz W220 petrol engine misfires and rough idle
The W220 petrol engine has misfires, what should be replaced?
If the spark plugs are the correct ones and intact, the ignition coils and spark plug leads are replaced next. When a fault code points to a specific cylinder, start with its coil. In the M113 engine the coils are separate, and one poor coil can take power away without a code.
How is cylinder-specific running smoothness checked?
The running smoothness test of a diagnostic tool shows per cylinder which cylinder runs unevenly, and also tells the condition of the ignition coils. If the test is fine but the vibration remains, the cause can be elsewhere, for example in the engine mounts.
The idle is rough and the warning light is on after replacing the mass air flow sensor, what is wrong?
A cheap aftermarket mass air flow sensor can be unreliable, and after fitting a Bosch part the car has worked normally. Read the fault code with a diagnostic tool before ordering the part, so that you replace the right one.