Idle Speed & Mixture

Connect tachometer to engine. Remove caps at exhaust manifold test points and connect CO meter. Warm engine to normal operating temperature and check ignition timing and idle speed. Adjust idle by turning idle air screw on throttle housing.

Fig 1: Adjusting Idle Speed at Throttle Housing
Courtesy of BMW OF NORTH AMERICA, INC.

Make adjustment before setting CO adjustment.
Measure CO level with engine idling. Disconnect oxygen sensor (plug below distributor on fender panel) and note CO reading. If level changes, adjustment is necessary. Do not accelerate engine while adjusting CO level.

Adjust mixture with Allen wrench through opening in fuel distributor (remove plug). After adjustment, reconnect oxygen sensor and ensure CO level does not change. Repeat procedure until both mixture and idle speed are correct.

Fig 2: Adjusting CO Level at Fuel Distributor

Courtesy of BMW OF NORTH AMERICA, INC.

Do not accelerate while making adjustments.

IDLE SPEED & CO LEVEL

Application

Idle RPM

CO%

Man. Trans.

800-900

⁽¹⁾ 0.2-1.2

Auto Trans.

900-1000

⁽¹⁾ 0.2-1.2

⁽¹⁾	Oxygen sensor disconnected.

FUEL PUMP PERFORMANCE

Application	Pressure psi (kg/cm² )	Volume in 30 sec. Pints (Liters)
All Models	64-74 (4.5-5.2)	1.6 (.75)