Smooth engine running analysis, function - GF07.61-P-3034AM
ENGINE 113.990 in MODELS 211, 219
ENGINE 113.991 in MODELS 215, 220
ENGINE 113.992 in MODEL 230
ENGINE 113.993 in MODEL 463
ENGINE 113.995 in MODEL 230
Engine running is constantly monitored in order to protect the catalytic converters from excessive thermal stresses if combustion misfirings occur. If the smooth engine running analysis detects combustion misfiring in the ME control unit, the appropriate fuel injector or injectors is or are no longer actuated after a certain number of misfirings. However at least two fuel injection valves are deactivated simultaneously.
The following combustion misfiring causes are detected:
- Ignition system
- Injection system
- Mechanical engine systems (e.g. valve seats, valve springs, fresh air)
- 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.
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
- Recognition of uneven road surface
- Synchronization of fuel injection and firing order
- Fuel reserve signal
- Sensor adaptation (crankshaft position sensor)
- Sensitivity of the acceleration measurement (adjustable with the STAR DIAGNOSIS)
- Engine speed, engine load
A comparative value for the time between two combustions is calculated from these two parameters.
- Recognition of uneven road surface
Vibrations transmitted through the drive train may have a negative influence on engine running at certain engine speeds and load states.
Thus on poor road surfaces the smooth engine running analysis is set to more sensitive.
The wheel speed signal (for detection of even wheel running) is received by the ME control unit via the CAN data bus from the ESP control unit.
- Synchronization of fuel injection and firing order
The cylinder recognition is required for storing and -evaluation.
- Fuel reserve signal
If combustion misfiring has been 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 ME control unit receives the information regarding the fuel level from the instrument cluster via the CAN data bus.
- Sensor adaptation
After successful adaptation of the crankshaft position sensor, 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 required as a comparison parameter for misfire detection.
- Misfire counter
The number of detected misfires is entered in the fault memory and differs by:
- Misfiring of specific cylinders
- Misfiring at "emission limit"
- Misfiring "harmful to TWC"
The smooth engine running analysis replaces the measurement of the combustion period and combustion voltage.
| Fuel injection valve, location/task/design/function | GF07.03-P-5004KE | ||
| Crankshaft position sensor, location/task/design/function | GF07.04-P-4116AM | ||
| Camshaft Hall sensor, location/task/design/function | GF07.04-P-4117HA | ||
| Pressure sensor, location/task/design/function | GF07.04-P-5014AM | ||
| Charge air temperature sensor, location/task/design/function | GF07.04-P-5039AM | ||
| ME-SFI control unit, location/task/design/function | GF07.61-P-5000AM |