Overrun Mode Fuel Shutoff, Function - GF07.10-P-1014MNL
Engine 176.9, 177.9 in model 217
Engine 176.9, 177.9 in model 222
Engine 177.9 in model 290
up to model year 2021
Function requirements for deceleration fuel shutoff, general points
- Circuit 87M (Engine management ON)
- Engine runs
- Accelerator not operated
- Gear range "D" or "R" is engaged
- Vehicle is not in cruise control mode
- Not too high an exhaust temperatures
Deceleration fuel shutoff, general
Deceleration fuel shutoff in deceleration mode of the engine has the following tasks:
- increasing the braking effect of the engine.
- reducing fuel consumption.
- improving exhaust characteristics.
The ME-SFI [ME] control unit (N3/10) performs a deceleration fuel shutoff dependent on the following sensors and signals:
- Coolant temperature sensor (B11/4), coolant temperature
- Accelerator pedal sensor (B37), accelerator pedal position
- Crankshaft Hall sensor (B70), engine speed
Deceleration fuel shutoff, function sequence
In overrun mode, the ME-SFI control unit switches off the fuel injectors for cylinders 1 to 8 (Y76/1 to Y76/8) depending on the coolant temperature, the engaged gear, and the engine speed if the accelerator pedal is not actuated.
The fuel injectors are switched on again when the accelerator pedal is operated.
The ME-SFI [ME] control unit also uses the left and right intake camshaft solenoids (Y49/4, Y49/5) and the left and right exhaust camshaft solenoids (Y49/6, Y49/7) to adjust the camshafts to a position with reduced valve overlap. This allows secure combustion without misfires.
After deceleration fuel shutoff, the ME-SFI control unit enriches the fuel/air mixture by briefly lengthening the injection period in order to relieve the catalytic converters of enriched oxygen.
To prevent an abrupt torque rise when combustion is restarted after the overrun mode fuel shutoff, the ME-SFI control unit briefly adjusts the ignition angles of the ignition coils for cylinders 1+2 to cylinders 7+8 (T4 to T4/3) in the direction of "retard". Deceleration fuel shutoff is disabled when exhaust temperatures are too high, since the high oxygen content occurring in the exhaust during a deceleration fuel shutoff could cause increased oxidation of carbon monoxide and hydrocarbon (afterburning). The heat so generated can overheat the catalytic converters.
| Electrical function schematic for deceleration fuel shutoff | Engine 177.9 in model 290 up to model year 2021 | PE07.10-P-2714-97XBA | |
| Engine 176.9, 177.9 in model 217 Engine 176.9, 177.9 in model 222 | PE07.10-P-2714-97SEL | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNL |