Smooth engine running analysis, function - GF07.10-P-1030M
ENGINES 275.950 in MODEL 215, 220
ENGINES 275.951 in MODEL 230 up to model year 2008 /AEJ 07
ENGINES 275.953 in MODEL 216, 221 up to model year 2008 /AEJ 07
ENGINES 275.954 in MODEL 230 up to model year 2008 /AEJ 07
ENGINES 275.980 in MODEL 215, 220
ENGINES 275.981 in MODEL 230 up to model year 2008 /AEJ 07
ENGINES 275.982 in MODEL 216, 221 up to model year 2008 /AEJ 07
ENGINES 285.950 in MODEL 240
ENGINES 285.980 in MODEL 240
To protect the catalytic converters from thermal overload through combustion misfiring and in order to keep the exhaust emission values, the engine operation is continuously monitored. If smooth engine running analysis in the ME-SFI [ME] control unit detects combustion misfiring, the fuel injection valves affected are no longer actuated after a certain number of misfiring.
The following combustion misfiring causes are detected:
- Ignition system
- Injection system
- Engine, mechanical aspects (e.g. fresh air, valve seat, valve springs)
- Fuel deficiency
Smooth engine running signal
For the smooth engine running analysis the signal supplied by the crankshaft position sensor is analyzed exactly in respect of time uniformity between the individual combustions by means of a comprehensive mathematical method.
- Engine speed, engine load
A comparative value for the time between two combustions is calculated from these two parameters.
Each individual combustion must produce a characteristic acceleration at the flywheel.
In case of combustion misfirings, the flywheel mass rotates slightly slower until the next ignition (short variations in torque).
The following factors are taken into account:
- Engine speed, engine load
- Engine temperature
- Recognition of uneven road surface
- Synchronization of fuel injection and firing order
- Fuel reserve signal
- Sensor wheel adaptation
- Engine temperature
If engine is cold, several combustion misfires are allowed temporarily.
- Recognition of uneven road surface
The wheel speed signal is sent via the CAN data bus from the ESP control unit (even running).
On poor road surfaces (washboard roads) the smooth engine running analysis is set less sensitive. Vibrations transmitted through the drive train may have a negative influence on the smooth operation analysis at certain engine speeds and load states.
- Synchronization of fuel injection and firing order
The cylinder recognition is required for fault storing and evaluation.
- Fuel reserve signal
If combustion misfires are detected, a fault is stored if the fuel tank level is too low. Combustion misfires due to fuel starvation are detected via this additional information.
The information about the fuel level is transferred via CAN data bus to the instrument cluster. From there the information passes via the CAN data bus to the ME-SFI [ME] control unit.
- Sensor wheel adaptation
After sensor adaptation is performed, the smooth engine running analysis becomes more sensitive and can be adapted to the specific smooth running properties of the engine.
During a deceleration phase (uniform smooth running) the smooth running analysis stores the particular smooth running properties of the engine. These are needed as comparative parameter to recognize combustion misfires.
- ECI ignition system
The results from the smooth operation and ionic current evaluation are combined to detect all combustion misfires reliably up to maximum engine speed.
Combustion misfire counter
The following information is entered in the fault memory:
- Sum of all combustion misfires
- Combustion misfires "cylinder-specific"
- "Emission limit" combustion misfires
- Combustion misfire "catalytic converter damaging"
For
the fuel reserve warning lamp is flashing, the purge system has a gross leak (e.g. tank lid missing).
If the fuel tank is filled to less than approx. 1/4 or to more than 3/4, the leak test of the fuel system is suppressed. A test for major leakage is still performed.
| ME-SFI [ME] control unit, location/task/ design/function | GF07.61-P-5000M |
| Crankshaft position sensor, location/task/ design/function | GF07.04-P-4116M |
| Camshaft Hall sensor, location/task/design/ function | GF07.04-P-4117M |
| Pressure sensor downstream of throttle valve actuator, location/task/function | GF07.04-P-5049M |
| Coolant temperature sensor, location/task/ design/function | GF07.04-P-5026M |
| Fuel injection valve, location/task/design/ function | GF07.03-P-5004M |