Cold Acceleration Enrichment

Fig. 2 Cold Acceleration Enrichment:

Fig. 7 Differential Pressure Regulator Test Setup:

Acceleration enrichment will only take place when the engine is below normal operating temperature, Fig. 14. The amount of enrichment is dependant on:
Engine coolant temperature
Movement of the sensor plate
Total travel of the sensor plate
Cold acceleration is only effective for a few seconds. The calibration of the air flow sensor potentiometer causes the enrichment to decrease as engine speeds increase.
1. Connect differential pressure regulator test harness (VW 1315A/1), Fig. 7, between the harness plug and the differential pressure regulator and hook up a multi-meter set for 0-200 mA.
2. Unplug harness connector from coolant temperature sensor and leave open.
3. Open throttle so that idle switch is open (no continuity).
4. Remove boot from air flow meter.
5. With ignition ON, quickly lift sensor plate fully and observe meter reading.
6. Current should briefly increase to at least 110 mA, then drop to 80 - 110 mA.
7. If current does not fall within specifications, check;
a. Air flow sensor potentiometer
b. Wiring circuit to control unit (terminals 14, 17, and 18 on control unit, and 3, 2, and 1 on potentiometer).
8. If circuits are OK, replace control unit.