SLK 230 (170.449) L4-2.3L SC (111.983) (2001)
Idle Speed: Description and Operation
ME-SFI Idle Speed Control Function
ENGINE 111.951 /952 /955 /956 /957 /958 /982 /983
B11/4
Coolant temperature sensor
B37
Pedal value sensor
M16/6
Throttle valve actuator
CAN
Controller area network (databus)
N3/10
ME control module
The throttle valve actuator controls the idle speed by altering the position of the throttle valve. It is actuated by the ME-SFI control module.
The ME-SFI control module actuates the throttle valve motor (M16/6m1) in line with the input signals received at the ME-SFI control module (N3/10).
The throttle valve actuator controls the idle speed
- different engine loads, e.g. power steering turned to full lock, engaging Drive position, switching on AC compressor
- different mixture, e.g. from activated charcoal canister if purging activated (depending on activated charcoal charge)
Heating-up speed
In order to warm up the catalytic converter more rapidly to operating temperature, engine speed is increased in the idle speed range to 1100 - 1500 rpm
for about 20 seconds after each engine start at coolant temperatures of < 40 °C. When a Drive position is engaged, engine speed is immediately
controlled to a lower value.
Automatic transmission
When a drive position is engaged, a lower engine speed is controlled in order to reduce the creeping tendency of the vehicle. The information "Drive
position engaged/not engaged" is transmitted by the ETC control module (N15/3) over the CAN databus to the ME-SFI control module.
Closed throttle
To assist the idle speed control, the ignition angle can be retarded by as much as 36° crank angle or advanced by as much as 20° crank angle from the
calculated specified value.