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Air Flow Sensor

The air flow sensor measures all intake air. Air flowing past the sensor plate lifts the plate which in turn lifts the control plunger in the fuel distributor to meter the fuel. The sensor plate and its cone-shaped venturi are designed to precisely match fuel delivery to air flow for all running conditions from idle to full throttle. Although they are seldom necessary as routine maintenance, there are several basic adjustments which may be necessary to assure proper operation if the assembly has been worn, damaged, or tampered with. These basic adjustments are only a starting point. Whenever such adjustments are made, the final step is to check and adjust idle mixture, as described in 6.7 Idle Specifications.

A sensor plate potentiometer provides the control unit with information on the position of the sensor plate. On CIS-E systems, this signal is used for cold acceleration enrichment. See 6.4 Electrical Tests (CIS-E). On CIS-E Motronic systems, the potentiometer signal to the control unit is used as an indication of load. See 6.5 Electrical Tests (CIS-E Motronic).

The sensor plate must be positioned correctly in the air cone and move with little resistance. If the sensor plate is off-center or binding in the air cone, or if the lever has too much resistance, fuel metering at the fuel distributor will be inaccurate or erratic.

To check the position and movement of the air flow sensor plate, the engine should be at normal operating temperature. Remove the rubber intake air boot from the top of the air flow sensor. The best test method, if possible, is to lift the plate by its center bolt using a magnetic tool. Lift the sensor plate slowly and make sure there is even resistance throughout the plate's entire range of travel. There should be no resistance as the sensor plate falls back to its rest position.

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