Federal
For best results, ignition timing, idle mixture (CO content), and base idle speed must be checked and adjusted simultaneously. Making these checks and adjustments together is very important in order to obtain satisfactory driveablity characteristics and emission levels.Final adjustment to the idle speed should be made only after the idle mixture is adjusted to specification. Final adjustments to the idle mixture (CO content) should only be made after the ignition timing is adjusted to specification.
Do not attempt to perform this operation without the necessary equipment.
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 raise the engine speed to a minimum of 2100 rpm four (4) times, letting the throttle close each time, (make sure engine has reached operating temperature).
NOTE: This clears the fault memory in the Digifant II control unit and cancels the hot-start idle increase function. This procedure must be repeated each time the vehicle is stopped and re-started during the test procedure.
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)
6. Reconnect the blue coolant temperature sensor.
IDLE/CO CONTENT
1. Start engine an let it idle.
2. Disconnect the blue coolant temperature sensor.
Idle Speed Boost Valves:
3. Disconnect the #1 boost valve harness connector. If car has A/C, disconnect #2 boost valve harness connector as well.
4. Disconnect and plug boost valve vacuum source hose "B".
5. Check that idle speed is within specification.
Idle Speed 900 ± 25 RPM
Idle Air Bypass Screw:
6. If not within specification, adjust using idle air bypass screw located on throttle housing.
7. Reconnect the blue coolant temperature sensor.
8. Check the idle speed.
Idle Speed 800 - 1000 RPM
9. Turn engine "OFF".
Crankcase Ventilation Hose:
10. Disconnect the crankcase ventilation hose from the emission control valve and plug the hose.
11. Start the engine and raise the engine speed to a minimum of 2100 rpm four (4) times, letting the throttle close each time, (make sure engine has reached operating temperature)
12. Disconnect the blue coolant temperature sensor harness connector while engine is idling.
13. Check the CO specification.
14. Record the CO value before adjusting.
Digifant II Idle CO Graph:
15. CO reading must fall within band on Checking Tolerance graph.
16. If CO reading does not fall within the tolerance band, proceed with adjustment.
Air Flow Sensor:
17. Remove the tamper-proof plug from the CO adjustment screw location on air flow sensor by drilling into plug with a:
0.098 in. (2.5 mm) drill bit
18. Thread a sheet metal screw into the drilled hole using a:
0.137 in. (3 mm) sheet metal screw
19. Pull out the screw (with plug attached) using pliers.
20. Adjust the CO as necessary by adjusting the CO adjustment screw in the air flow sensor with a:
5 mm hex wrench
21. Adjust the CO content according to the Adjusting Specification graph.
22. Reconnect harness connector.
NOTE: Fan must not be running while reconnecting.
23. Reconnect the idle boost valve harness connector and hose.
24. Reconnect crankcase ventilation hose.
25. Start the engine and recheck idle speed and CO%.
Idle Speed 800 - 1000 RPM
CO Content 0.3 to 1.2% at any altitude
FINAL CHECK
1. Install a new tamper-proof plug over the CO adjustment screw, if it was removed.
2. Disconnect the test equipment, check all hose and electrical connections and reinstall CO tap cap.
3. 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.
4. 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.
5. After road test check for fault codes.
6. 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.
7. If only the idle CO% is NOT OK:
a. Check the oxygen sensor system. Refer to COMPUTERIZED ENGINE CONTROLS.
8. If the idle speed and idle CO% are NOT OK:
a. Check the coolant temperature sensor and wiring. Refer to COMPUTERIZED ENGINE CONTROLS.