Airflow Sensor & Mixture Control Unit
- On 911 series, 924, and Turbo Carrera, remove air cleaner assembly. Working through air inlet opening, raise sensor plate lever from below. On other models, push down on sensor plate from above. Resistance to sensor plate movement should be even and constant throughout entire range of travel.NOTE: On 911 series, 924 and Turbo Carrera, air flow is upward around sensor plate. On 928 and 930 Turbo models, air flow is downward. See Fig 1.
- On all models, loosen line to control pressure regulator at fuel distributor to relieve fuel pressure. Upper edge of sensor plate should be flush with lip of venturi.
- On 924 and Carrera, adjust height of sensor plate by bending wire bracket beneath sensor plate. On 911 series, a screw and lock nut assembly is used to adjust sensor plate height. A rubber stopping block limits downward movement of lever.NOTE: On 928 and 930 Turbo, the spring-loaded sensor plate stop is set at factory and cannot be adjusted.
- Now check sensor plate position with control pressure applied. Turn ignition on and disconnect airflow sensor. If sensor plate raises slightly on (drops slightly on 911 series, 924 and Carrera) by a maximum of 0.04" (1 mm), operation is satisfactory.
- Plate may not move at all under control pressure and this condition is also satisfactory. See Fig 1. If necessary, replace leaf spring on sensor plate stop.
- To center sensor plate within air cone, remove retaining bolt. Coat bolt threads with locking compound and install bolt finger tight. Using a feeler gauge, center sensor plate so that a 0.004" (0.10 mm) gap exists between plate and air cone wall. Tighten retaining bolt to 43-48 INCH lbs. (4.9-5.4 N.m). Recheck gap after tightening.