Idle Speed: Testing and Inspection

Checking engine idle speed and exhaust gas contents (M50,M52,S50,S50US) - vehicle with catalytic converter -







Requirements for all adjustments:
Engine at normal operating temperature (oil temperature > 60° C).
Engine and ignition system functioning correctly.

Connect up BMW Service Tester.
Check idling speed:
Engine Test, Test Step No. 5

Interrogate fault memory of DME control unit.
1) Engine idle speed:
Check engine idle speed.

2) Exhaust test:
Insert exhaust sensor in exhaust tailpipe.
Check exhaust contents at idle speed.
Switch off exhaust extraction system for time of testing.
If nominal value is not achieved, exhaust contents can also be measured on each individual cylinder group.


If the exhaust idling speed values deviate from specified value:
Interrogate the fault memory of the Digital Motor Electronics.
If the Lambda oxygen sensor fault memory is set to Lambda regulation, troubleshooting must be continued using special tool 11 7 450 (Lambda oxygen sensor tester).







If exhaust gas measuring screws are installed in the manifold:
Measure exhaust content in front of catalytic converter.
Unscrew bolts (1).







Connect special tool 13 0 080 to exhaust manifold.
Connect measuring sensor on exhaust tester to special tool 13 0 080.
Switch off exhaust extraction system for time of testing.


3) NOTE: Before correcting the exhaust/idle setting, first ensure that there are no malfunctions on the engine, in the ignition system or the fuel injection system.

For example, if the exhaust/idling speed value is too high:
- Check injector nozzles.
- Check fuel delivery pressure.
- Check coolant-temperature sensor.
- Check air intake system for leaks.
- Check idling speed valve.

For example, if the exhaust/idle value is too low:
- Check hoses and connections for idling speed control and localize the air leak.
- Check air intake system for leaks.
- Check idling speed valve.