ME idle speed control, function - GF30.22-P-0003GS

ENGINE 111.951 /952 /955 /956 /957 /958 /982 /983 

Fig 1: ME Idle Speed Control Function Diagram

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.

AC compressor 

In order to avoid engine speed dropping in the idle speed range when the AC compressor is engaged, the AC push-button control module (N19) or automatic air conditioning push-button control module (N22) supplies a signal to the ME-SFI control module (over CAN) and the opening cross-section of the throttle valve is enlarged.

Idle speed can be influenced with the STAR DIAGNOSIS.