Idle Stabilization (Digifant II)

DIGIFANT II

Idle Stabilization - Checking

Requirements

- Engine oil temperature is at least 80°C (176°F).
- Basic engine settings checked and idle speed not within specifications.
- Coolant temperature sensor and wiring OK.
- Idle switch and wiring OK.
- All electrical consumers switched OFF (coolant tan must not run during checking or adjusting).
- Connect VW 1367 engine tester.
- Connect digital multimeter to idle stabilizer using adapter Vw 131 5A/2. Set meter to 5 or 10 amp. scale (reading will be in milliamps).
- Start engine and raise speed to a minimum of 2100 RPM tour times, letting the throttle close each time.

Note: This must be repeated each time the engine is stopped and re-started.

- Disconnect the coolant temperature sensor and observe stabilizer control current.
- Specification: Approximately 430 mA and fixed (non-fluctuating).

If control current is not OK,

- Check continuity of the wiring from the idle stabilizer to terminals 22 and 23 of the Digifant E.C.U.

It the continuity is OK,

- Replace the Digitant E.C.U. and re-test.
- Observe the idle RPM.
- Must be 975 ± 50 RPM.

If not OK,

- Adjust by turning the idle-air bypass screw on the throttle body.
- Reconnect the coolant temperature sensor and observe the readings.
- Idle speed must drop to 800 ± 50 RPM.
- Stabilizer control current must drop to 400 ± 20 mA.

It not OK,

Idle RPM is OK, but control current is high:

- Probable engine vacuum leak.
- Locate and repair.

Idle RPM is OK but control current is low, or idle RPM is high and control current is OK or low

- Stabilizer valve is sticking open.
- Clean or replace stabilizer valve. (Check adjustment if valve has been modified.)

Idle RPM is low, and control current is high:

- Stabilizer valve is sticking shut.
- Modify stabilizer valve as per Croup 24 of Technical Information.

Milliamp Increase While Cranking Starter

Requirements

- Idle stabilizer valve OK (the valve must vibrate and hum with the engine running).
- Connect digital multimeter to idle stabilizer using adapter Vw 131 5A/2. Set meter to 5 or 10 amp. scale (reading will be in milliamps).
- Ground ingnition coil terminal #4.
- Crank engine.
- Stabilizer current should Increase beyond 430 mA while cranking starter.

If not OK,

- Disconnect multi-pin connector from the Digitant E.C.U.
- Check continuity of wire from terminal 1 of E.C.U. connector to terminal 50 of starter motor.

If the continuity is OK,

- Replace the Digifant E.C.U. and retest.

Milliamp Increase for A/C Operation

Requirements

- Idle stabilizer valve OK (the valve must vibrate and hum with the engine running).
- Connect digital multimeter to idle stabilizer using adapter VW 131 5A/2. Set meter to 5 or 10 amp. scale (reading will be in milliamps).
- Start engine and raise speed to a minimum of 2100 RPM four times, letting the throttle close each time.
- With engine idling, observe milliamp reading at the idle stabilizer.
- Switch the A/C ON.
- Milliamp reading must increase by approximately 150 mA when the A/C compressor is engaged.

If there is no milliamp increase,

- Stop the engine.
- Disconnect the multi-pin connector from the Digifant E.C.U.
- With the ignition and A/C switched ON, check for 12 volts at terminal 16 of the Digifant E.C.U. connector.

If there is not 2 volts at terminal 16 of the Digifant E.C.U. connector,

- Repair the wiring between terminal 16 of the Digifant E.C.U. connector and the A/C thermostat on the evaporator. (See the wiring diagram)

If there is 12 volts at terminal 16 of the Digifant E.C.U. connector,

- Replace the Digifant E.C.U. and re-test.