California
Air/fuel mixture and idle speed is always controlled by the Digifant I control unit. The purpose of the idle mixture adjustment is to fine-tune the mechanical adjustment of the air flow sensor and match it to the electronic controls. The C.O. adjustment screw does not affect the actual air/fuel mixture, nor does the idle air bypass screw affect the actual idle speed.Making these checks and adjustments together is very important to both driveablity and emissions control. If the equipment necessary to accurately perform this work is not available, we suggest turning the job over to a local repair shop that has the needed test equipment. In a properly equipped shop, these checks and adjustments can be made quickly, accurately, and at resonable cost.
NOTE: The first step in any Digifant I system troubleshooting must be to check the control unit fault memory, find and correct any faults that may be indicated, then erase the fault memory before continuing with testing procedures. For more information Refer to COMPUTERIZED ENGINE CONTROLS
Check and adjust the basic engine settings in the following order:
1. Ignition timing
2. CO content
3. Idle speed
4. Final check of specifications
TEST AND ADJUSTMENT CONDITIONS
1. Engine oil temperature must be at least 176° F (80° C) and radiator cooling fan has operated at least once.
2. All electrical consumers switched "OFF" (radiator cooling fan must not be running during checking or adjusting).
3. A/C switched "OFF".
4. Idle switch is functioning properly.
5. Idle stabilization system operating properly.
6. The exhaust system must be free of leaks.
7. There must be no engine vacuum leaks.
8. The oxygen sensor must be operating properly.
TEST AND ADJUSTMENT SET-UP
1. Turn ignition switch "OFF".
2. Connect VW 1367 engine tester (or suitable timing light and tach.)
3. Connect an EPA approved CO tester to the CO tap tube using VW special tool #6006-0019 high temperature silicone connecting hose, (or equivalent).
NOTE: Non-approved connecting hoses may dramatically alter your readings.
IGNITION TIMING
1. START the engine and let it idle
Coolant Temperature Sensor Location:
2. Disconnect the blue harness connector from the engine coolant temperature sensor.
Ignition Timing Mark:
3. Increase the engine speed to 2300 ± 50 rpm and check the ignition timing. Specifications are:
Checking: 4° to 8° BTDC
Adjusting: 6° ± 1° BTDC
4. If adjustment is necessary, loosen the distributor clamp bolt and rotate the distributor until specification is correct.
5. Tighten the distributor clamp bolt to:
18 ft.lb. (25 Nm)
5. Reconnect the blue coolant temperature sensor. Fault code 2312 is generated whenever the coolant temperature sensor is disconnected. Refer to COMPUTERIZED ENGINE CONTROLS for reset procedures.
IDLE/CO CONTENT
1. Start engine an let it idle.
2. Disconnect blue coolant temperature sensor harness connector.
NOTE: DO NOT attempt to adjust the idle speed using the idle air bypass screw. Idle speed is computer controlled.
3. Check idle speed and the CO specification after engine has run approximately 1 minute (cooling fan has cycled at least once).
0.3 to 1.2 vol.% at 800 - 1000 RPM
4. Record the CO value before adjustment.
5. If not within specification, use the following procedures.
Idle Speed Boost Valves:
6. Disconnect the #1 boost valve harness connector. If car has A/C, disconnect #2 boost valve harness connector as well.
7. Disconnect and plug boost valve vacuum source hose "B".
8. Check that idle speed is within specification.
Idle Speed 900 ± 50 RPM`
Digifant I Throttle Valve:
9. If not within specification, adjust using idle air bypass screw located on throttle housing.
10. Start the engine and let it idle.
11. Reconnect the blue temperature sensor harness connector.
12. Check that idle speed is within specification.
Idle Speed 800 - 1000 RPM
13. Turn engine "OFF".
Crankcase Ventilation Hose:
14. Disconnect the crankcase ventilation hose from the emission control valve and plug the hose.
15. Start the engine and let it idle until cooling fan cycles at least once.
16. Disconnect the blue coolant temperature sensor harness connector.
17. Reconnect harness connector after 1 minute.
NOTE: Fan must not be running while reconnecting.
18. Turn ignition "OFF".
19. Reconnect the idle boost valve harness connector and hose.
20. reconnect crankcase ventilation hose.
21. Start the engine and recheck idle speed and CO%.
Idle Speed 800 - 1000 RPM
CO Content 0.3 to 1.2%
22. Fault code 2312 is generated whenever the coolant temperature sensor is disconnected. Refer to COMPUTERIZED ENGINE CONTROLS for reset procedures.
FINAL CHECK
1. Disconnect the test equipment, check all hose and electrical connections and reinstall CO tap cap.
2. Road test vehicle for 10 minutes. Coolant temperature must be over 176°F (80°C) for at least 3 minutes before testing. Try to duplicate original complaint.
3. During test drive, perform the following operations:
a. With engine speed over 4600 RPM, push gas pedal to full down position briefly.
b. While driving at 30 Mph (50 Km/h) in 4th gear, accelerate with gas pedal pushed halfway down for about 4 seconds.
4. After road test check for fault codes.
5. If only the idle speed is NOT OK:
a. Check the throttle position sensor and wiring. Refer to COMPUTERIZED ENGINE CONTROLS.
b. Check the idle stabilization system. Refer to COMPUTERIZED ENGINE CONTROLS.
6. If only the idle CO% is NOT OK:
a. Check the oxygen sensor system. Refer to COMPUTERIZED ENGINE CONTROLS.
7. If the idle speed and idle CO% are NOT OK:
a. Check the coolant temperature sensor and wiring. Refer to COMPUTERIZED ENGINE CONTROLS.