# Adjusting CO

Engine must be at normal operating temperature

Idle speed at 880 ± 50 rpm

Pull off purge line at charcoal canister and remove the tamper proof plug from the airflow meter.

Connect the probe from a gas analyzer to the exhaust.

Check CO and note the measured value, with oxygen sensor connected. The CO value must be within the range of 0.2% - 1.2%
Determine correct operation of oxygen sensor by removing and plugging vacuum line from fuel pressure regulator. If the oxygen sensor is operating, the gas analyzer will show the CO rise, then fall back to the original level. If oxygen sensor is working, continue. If it is not working, replace before continuing.

Disconnect the oxygen sensor and check CO value again.

Compare this value with the CO value measured with the oxygen sensor connected.

If any deviation is observed, adjust the CO volume by turning the air by-pass screw on the airflow meter to the correct value.

Make adjustments slowly and allow time for the system to settle before continuing adjustment.

When the reading is between 0.2% - 1.2% with the oxygen sensor disconnected, reconnect sensor and purge line. Replace tamper proof plug.

E30 M3 Repair Manual V2.7. Copyright ©1999-2001 Koala Motorsport & Brett Anderson