Smooth engine running analysis, function engine 113 - GF07.61-P-3034SM
ENGINE 113.986
ENGINE 113.987
ENGINE 113.988
ENGINE 113.989
Engine running is constantly monitored in order to protect the catalytic converter from excessive thermal stresses if combustion misfiring occurs. If the smooth engine running analysis detects combustion misfiring in the ME control unit (N3/10), the appropriate fuel injector or injectors (Y62) 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
- Engine mechanical faults (e. g. valve seat, valve springs, fresh air)
- Fuel deficiency
Smooth engine running signal
For the smooth engine running analysis the signal supplied by the crankshaft position sensor (L5) 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
- Detection of road bumps
- Synchronization of injection and firing order
- Fuel reserve signal
- If sensor adaptation is performed (crankshaft position sensor)
- Sensitivity of the acceleration measurement (adjustable with 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
The wheel rpm signal (equal running) is received by the ESP and BAS [ESP, PML and BAS] control unit () via the CAN databus.
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 evaluation at certain engine speeds and load states.
- 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 (A1) via the extremely fast data bus called CAN.
- Sensor rotor adaptation (crankshaft position sensor)
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 required as a comparison parameter for detecting misfiring.
- 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 valves, component description | Y62 | GF07.03-P-6010SM | |
| Crankshaft position sensor component description | L5 | GF07.04-P-6010SM | |
| Camshaft Hall sensor component description | B6/1 | GF07.04-P-6020SM | |
| Hot film MAF sensor component description | B2/5 | GF07.07-P-6000SM | |
| ME-SFI [ME] control unit component description | N3/10 | GF07.61-P-6000SM | |
| Component description of ignition coil | T1/1-T1/8 | GF15.10-P-2100SM | |
| Accelerator pedal sensor, component description | B37 | GF30.20-P-2010SM | |
| Component description of fuel level sensor | B4 | Model 171, 215, 220 | GF47.10-P-2010SM |
| B4/1, B4/2 | Model 203, 209 |