Idle Mixture & Co Level

NOTE: Mixture adjustment is NOT a normal tune-up procedure. Mixture adjustment should not be performed unless mixture control unit is replaced or vehicle fails emissions testing.

Warm engine to normal operating temperature. Check idle speed and ignition timing. Disconnect oxygen sensor. Check CO level.
If CO level is incorrect, turn off engine. Drill two 5/16" holes in adjustment plug. Pull out plug with snap ring pliers. Start engine and adjust CO level. See Fig 1 .

Fig 1: Idle Mixture Adjustment (740 Turbo, 760 GLE & 760 Turbo)
Courtesy of VOLVO CARS OF NORTH AMERICA.
Turning screw counterclockwise decreases CO level. Turning screw clockwise increases level. When adjustment is completed, reconnect oxygen sensor lead and remove test equipment. Seal CO adjustment screw with a new plug.

IDLE SPEED & CO LEVEL

Application

Idle RPM

% CO Level

740 Turbo, 760 GLE & 760 Turbo

750

⁽¹⁾ 0.6

⁽¹⁾	O2 sensor disconnected. CO level is measured before catalytic converter.