Idle Speed, Testing

Idle Speed, Checking

Special tools and equipment






- VAS5051 with VAG5051/1

or

- VAG1551 with VAG1551/3B

Test requirements
- Exhaust system free of leaks.
- Coolant temperature at least 80 degree C.
- Electrical consumers switched off (radiator fan must NOT run during test).
- A/C switched off.
- No pressure gauges (e.g. for fuel pressure test) connected.

NOTE:
- Idle speed cannot be adjusted.
- Idle speed is checked during basic setting of the engine.
- During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve (EVAP valve -N80-) is closed and the A/C compressor is switched off

Test sequence
- Check DTC Memory. There must not be any DTCs stored. Repair malfunctions if necessary, erase DTC memory, switch engine off and start again, road test vehicle and check DTC memory again as a control measure.
- Let engine continue to run at idle.

CAUTION: Electric radiator fan must not run.

Indicated on display:


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -4- to select "Initiate Basic Setting" and press -Q- button to confirm input.

Indicated on display:


System in Basic Setting Q
Input display group number XXX


- Press buttons -0-, -5- and -6- to select "display group number 056" and press -Q- button to confirm input.

Indicated on display:


System in Basic Setting 56 ->
1 2 3 4


- Check whether the engine speed in display field 1 (actual engine speed) is within tolerated range.

Display Group 056:

NOTE:
- Engine speed in display field 1 (actual engine speed) is the current engine speed.
- Engine speed in display field 2 (specified engine speed) is a theoretical engine speed calculated by the ECM.
- At idle, the ECM always attempts to adapt the engine speed (actual) to the specified engine speed (specified).
- This means that the engine speed (actual) must always approximately match the engine speed (specified) at idle.
- Display fields 3 and 4 provide information, but are not relevant for checking idle speed.

If specified value is obtained:
- Press -> button.

Indicated on display (function selection):


Rapid data transfer HELP
Select function XX


If specified value is not obtained:
- Check DTC memory again.

If idle speed is too high or low and there are no DTCs in DTC memory, the following tests (marked with dots) must be performed:
- False air in intake air system, checking. Intake System, Checking For Leaks (Unmetered Air)
- Check throttle valve control module Throttle Valve Control Module -J338-, Checking
- Evaporative Emission (EVAP) canister purge regulator valve always open, checking. Canister Purge Control Valve
- Perform adaptation of throttle valve control module.

Significance of 5 digit indication of display group 056