Fuel - Idle Mixture Check/Adjustment Manual Suppliment
87bmw10GROUP 13 Fuel Systems
Bulletin Number 13 02 87 (1348) Page 1 of 1
Montvale, NJ April 1987 Technical Dept.
SUBJECT: Idle Mixture Check and Adjustment (after major engine repair)
MODELS: M3, M5, M6
Situation: After a major engine repair, it might be necessary to check and adjust the idle mixture. The specific procedures as outlined in the Repair Manual apply only to cars on which each exhaust manifold pipe is equipped with its individual CO-screw.
Follow the procedure outlined below for idle mixture check and adjustment for M3, M5 and M6 cars that don't have CO-screws on the exhaust manifold pipes.
Procedure: General Requirements
^ Engine at operating temperature, i.e. oil temperature at least 60~C/140~F.
^ Ignition timing and valve clearance correct.
^ Correct throttle plate synchronization.
^ Idle speed correct.
^ All electrical consumers and air conditioner shut off. (For details refer to Nominal Values and Repair Manual)
Idle Mixture Adjustment
^ Connect Digital Mixture Measurement Unit (integrator voltage measuring unit for 318i - P/N 88 88 6 126 400) to engine diagnosis socket (BMW Service Tester cable connected to Digital Mixture Measurement Unit).
^ Start engine.
^ Flashing of the red LED at regular intervals indicates normal operation of the oxygen sensor.
^ Read integrator voltage on LCD display. If necessary, adjust to a value of 6 +/- 3 volts at the airflow meter bypass screen while the red LED pulsates at a regular interval.
^ If red LED stays "on" continuously, engine idle speed mixture is too lean or oxygen sensor is defective.
^ If red LED stays "off" continuously, engine idle speed mixture is too rich.
^ Adjust idle mixture by carefully turning the airflow meter bypass screw (see Repair Manual) to a value of 6 +/- 3 volts, until the LED flashes at a regular interval.
^ Check engine idle speed and integrator voltage.