Ignition System: Adjustments

For best results, ignition timing, idle fuel mixture (% CO), and idle speed must be checked and adjusted together. Final adjustment to idle speed should be made only after idle mixture is adjusted to specification. Final adjustments to idle mixture (% CO) should only be made after ignition timing is adjusted to specification.

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.

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. For more information refer to COMPUTERS AND CONTROL SYSTEMS.
5. Idle stabilization system operating properly, the valve must vibrate and hum while the ignition is ON. For more information refer to COMPUTERS AND CONTROL SYSTEMS.
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. For more information refer to COMPUTERS AND CONTROL SYSTEMS.

TEST AND ADJUSTMENT SET-UP

1. Turn ignition switch OFF.
2. Connect VW 1367 engine tester (or suitable timing light and tach.)
3. Remove the cap from the CO tap tube that comes from the exhaust manifold and 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 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 ECM 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 Connector:

2. Disconnect harness connector from engine coolant temperature sensor.
3. Increase engine speed to 2300 ± 50 rpm and check ignition timing. Specifications are:

Checking: 4° to 8° BTDC
Adjusting: 6° ± 1° BTDC

4. If adjustment is necessary, loosen distributor clamp bolt and rotate distributor until specification is correct.
5. Tighten distributor clamp bolt to:

18 ft.lb. (25 Nm)

CO CONTENT

Coolant Temperature Sensor Connector:

1. Disconnect coolant temperature sensor.
2. Raise dipstick slightly to allow for crankcase ventilation.

Crankcase Ventilation Hose:

3. Disconnect the crankcase ventilation hose from the emission control valve and plug the hose.

Idle CO And Idle Speed Adjustments:

4. Adjust idle speed using idle air bypass screw to:

800 ± 50 rpm

NOTE: This idle speed setting is used only for CO adjustment. The idle speed must be adjusted to a different specification after adjusting CO volume.

5. Check CO specification.
6. Record CO value before adjusting.

Digifant II Idle CO Graph:

7. CO reading must fall within band on Checking Tolerance graph.
8. If CO reading does not fall within tolerance band, proceed with adjustment.
9. Remove tamper-proof plug from CO adjustment screw location on air flow sensor by drilling into plug with a:

0.098 in. (2.5 mm) drill bit

10. Thread a sheet metal screw into the drilled hole using a:

0.137 in. (3 mm) sheet metal screw

11. Pull out the screw (with plug attached) using pliers.
12. Adjust CO as necessary by adjusting CO adjustment screw in air flow sensor with a:

5 mm hex wrench

13. Adjust CO content according to Adjusting Specification graph.

IDLE SPEED

1. Remove plug from crankcase ventilation hose and connect hose to emission control valve.
2. Re-seat oil level dipstick.
3. Adjust idle speed using idle air bypass screw. Adjust idle speed to:

975 ± 50 rpm

FINAL CHECK

1. Reconnect harness connector to coolant temperature sensor.
a. Idle speed must drop to:

800 ± 50 rpm

b. Idle CO must be:

0.7% ± 0.4% at any altitude

2. Install new tamper-proof plug over CO adjustment screw, if it was removed.
3. Disconnect test equipment, reinstall CO tap cap.
4. If only the idle speed is NOT OK:
a. Check idle switch and wiring (1).
b. Check idle stabilization system (1).

5. If only the idle CO% is NOT OK:
a. Check the oxygen sensor system (1).

6. If the idle speed and idle CO% are NOT OK:
a. Check the coolant temperature sensor and wiring (1).

(1) Refer to COMPUTERS AND CONTROL SYSTEMS.