Test Point 12 - CO and Idle Speed Adjustments
TEST POINT 12 - DME 944CO Level and Engine Idle Speed Adjustments
It is important that the engine have operating temperature for the following tests, in particular checking or adjusting engine idle speed as well as CO level adjustments. On the other hand the intake pipes must not be heated excessively, since this would produce wrong test values or make it impossible to adjust the engine.
Operating temperature means: Engine temperature = approx. 90 °C
Intake air temperature = approx. 15 - 35 °C
All equipment switched off.
CO Level: 1 ± 0.5% at idle speed (840 ± 40 rpm) and with equipment switched off.
0.6 ± 0.2% for USA cars or cars with unleaded gasoline engines, measured in front of catalytic converter.
Idle Speed: Bridge test socket term. B and C on regulator plate.
Adjust idle speed to 840 ± 20 rpm on bypass air screw of throttle housing, with equipment switched off.
Remove bridge on test socket. Accelerate engine briefly and check idle speed (840 ± 40 rpm).
Adjusting Procedures:
USA Cars/Unleaded Engines M 298/M 299
Exhaust gas tested in front of catalytic converter on test pipe in engine compartment, on right hand side.
Pull off plug on oxygen sensor.
Check or adjust idle speed CO level.
Specification: 0.6 ± 0.2 % CO (at 840 ± 40 rpm).
Accelerate engine briefly after each adjustment.
Connect plug on oxygen sensor.
Bridge term. B and C on test socket of regulator plate.
Check/adjust engine idle speed.
Specification: 840 ± 20 rpm.
Adjust idle speed on bypass air screw of throttle housing.
Remove bridge on test socket. Accelerate engine briefly.
Check CO level and idle speed.
Plug exhaust test pipe.