Idling Speed, Checking

Idling speed, checking

Test conditions
- No leaks in exhaust system
- Coolant temperature at least 85 degrees C.
- Electrical consumers switched off (radiator fan must not run during the check)
- Air conditioner switched off
- Pressure gauge not connected
- Place selector lever in P or N position (vehicles with automatic transmission)

Checking idling speed

NOTE:
- The idling speed cannot be adjusted.
- The idling speed is tested during the basic setting of the engine.
- During the basic setting of the engine, the air conditioner compressor is automatically switched off and the EVAP canister purge regulator valve is closed.

- Check Diagnostic Trouble Code (DTC) memory. DTC memory must be clear. If necessary, correct any malfunctions and erase DTC memory.
- Switch engine off, then start up again. Perform road test and check DTC memory again to make sure it is clear.
- Start engine and run at idling speed.
- Switch off air conditioner.
- Switch off rear window defroster.
- Position selector lever in P or N position (vehicles with automatic transmission).

CAUTION: The electric radiator fan should not be running.

Indicated on display


Rapid data transfer HELP
Select function XX


- Press keys 0 and 4 for function "Introduction of basic setting" and confirm entry with Q key.

Indicated on display


Basic setting
Enter display group number XXX


- Press keys 0, 5 and 6 for "display group number 56" and confirm entry with Q key.

NOTE:

Indicated on display: (1...4 display zones)


System in basic setting 56 ->
1 2 3 4


- Check whether engine speed in display zone 1 (actual speed) is within permitted tolerance range (670 rpm to 850 rpm).

Display Group 56:

- During idling, the engine control module always tries to adapt the actual engine speed to the specified engine speed.
- This means that during idling the actual engine speed must always approximate the specified engine speed.
- The display zones three and four are there for information but are irrelevant for checking the engine idling speed.

- Press ->key.
- Press keys 0 and 6 for "End output" function and press Q key to confirm entry.
- If specification is not attained, check DTC memory again.
- If DTC memory was erased, readiness code must be re-generated. Readiness Code, Generating


If the idling speed is too high or too low or not smooth and there are no DTCs recorded in the DTC memory, perform the following tests marked with a dot:

- Check oxygen sensor learned values and oxygen sensor control. Oxygen Sensor Before Catalyst, Checking
- Check for unmetered air in intake system.
- Check whether EVAP canister purge regulator valve is continuously open. EVAP Canister Purge Regulator Valve -N80-, Checking
- Perform adaptation of throttle valve control module.

Meaning of 5 digit readout of display group 56

Meaning of 5 digit readout of display group 56: