Idle Mixture

NOTE: Adjustment is not a normal tune-up procedure and should not be performed unless vehicle fails emission testing.

On CIS models, remove mixture control unit, separate control unit and drive out mixture plug (steel ball) with a punch. Reassemble control unit and reinstall.
On LH-Jetronic models, remove the aluminum/steel plug from air mass meter to gain access to mixture screw. On all models, disconnect oxygen sensor connector. Remove plug from exhaust pipe (in front of converter) and insert CO meter probe.
If CO reading is not within specifications, insert adjusting wrench (5015) or screwdriver (LH-Jetronic models only) into adjustment hole and adjust CO reading to specifications.
Reconnect oxygen sensor electrical connector and check CO reading. Repeat adjustment procedure if necessary. See Fig 1 . After each adjustment, remove adjusting wrench and cover adjustment hole. This will prevent a lean mixture while checking CO level.

After CO adjustment, remove test equipment. Insert exhaust pipe plug and seal mixture adjustment hole.

IDLE SPEED & CO LEVEL

Application

Idle RPM

⁽¹⁾ CO%

Non-Turbo

CIS Injection

750

0.7-1.3

LH-Jetronic Inj.

750

0.4-0.8

Turbo

900

0.7-1.3

⁽¹⁾	With oxygen sensor disconnected. Less than 1% with oxygen sensor connected.

Fig 1: Idle Mixture Adjustment

Courtesy of VOLVO CARS CORPORATION

Fig 2: Idle Mixture Adjustment

Courtesy of VOLVO CARS CORPORATION