Computers and Control Systems: Adjustments

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 (differential pressure regulator current)
3. Idle speed (idle stabilizer valve duty cycle)
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. Idle switch is functioning properly.
4. Idle stabilization system operating properly, the valve must vibrate and hum while the ignition is "ON".
5. A/C switched "OFF".
6. The exhaust system must be free of leaks.
7. There must be no engine vacuum leaks.
8. The oxygen sensor must be connected and operating properly.
9. No fuel pressure measuring equipment connected.
10. If injector lines were loosened or replaced, run the engine up to 3000 rpm several times and then allow to idle for at least 2 minutes before performing any adjustments.
11. Throttle cable adjustment must be OK.

TEST AND ADJUSTMENT SET-UP

1. Put vehicle in PARK or NEUTRAL and set the parking brake.
2. Turn ignition switch "OFF".

Checking Motronic Ignition:

3. Connect VAG 1367 engine tester using VAG 1367/8 inductive pickup, or suitable timing light and tach.
4. 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. Adaptor must be connected tightly to CO tap tube to prevent measuring errors.

5. Remove tamper proof plug from air flow sensor assembly.

Crankcase Housing Breather Hoses:

6. Disconnect crankcase housing breather hoses #1 and #2 from breather housing #3 and place hoses such that only fresh air can be drawn in. Calibrated insert #4 must be disconnected from hose #2.

Charcoal Canister "T" Fitting:

7. Remove the charcoal canister line "T" fitting from the air flow sensor boot, rotate the "T" 90° and reinstall with blank port (0.059 in. /1.5 mm) back into the boot. If the car is not equipped with the "T" fitting, remove the hose and fit a restrictor plug with a 0.059 in. (1.5 mm) hole. Such a plug is available from VOLKSWAGEN.
8. Ensure that ignition switch is turned "OFF".
9. Disconnect the harness connector from the differential pressure regulator.

Diaphragm Pressure Regulator Testing Connections:

10. Connect test adaptor VAG 1315A/1 (or equivalent) between the differential pressure regulator and the harness connector.
11. Switch a suitable multimeter such as the Fluke 83 multimeter to 200 mA range.
12. Connect the multimeter to test adaptor VAG 1315A/1 or equivalent, using jumper wires from VW 1594 adaptor kit.
13. Turn the ignition switch "ON".
14. Control current must be displayed as a positive polarity. If negative polarity is displayed, reverse the multimeter test leads.
15. Turn the ignition switch "OFF".
16. Connect a duty cycle meter, such as the Siemens 451, to the test connector in the wiring harness near the ignition coil, (connector contains blue/gray wire). Connect the duty cycle meter according to the instrument manufacturer's instructions. A common dwell meter can also be used to measure the idle stabilizer valve duty cycle. The 90° scale of a dwell meter corresponds to the 100% scale of a duty cycle meter. Multiply the duty cycle specifications by 0.9 to get the corresponding value for a dwell meter. For example, a 50% duty cycle would read as 45° on a dwell meter. The tests below give specifications for both instruments. Connect a dwell meter by connecting the meters positive (+) lead to the test connector near the coil (with blue/gray wire) and the negative (-) lead to ground.

TEST AND ADJUSTMENT PROCEDURE

IGNITION TIMING

1. START engine and let it idle.
2. Check the ignition timing, checking value is:

4° to 8° BTDC

3. Adjust the ignition timing if needed.
4. Loosen the distributor and rotate until specification is correct, adjusting value is:

6° ± 1° BTDC

5. Tighten the distributor bolts to:

18 ft.lb. (25 Nm)

CO CONTENT

1. Check the CO content before adjusting and record the value.
2. To accurately check the CO content idle must be:

800 to 1000 rpm

3. Check the differential pressure regulator control current, checking value is:

4 to 16 mA (must fluctuate)

CIS-E CO Adjustment Screw:

4. If adjustment is needed, adjust the differential pressure regulator control current using a long 3mm hex wrench in CO adjusting screw, adjusting value is:

10 ± 1 mA (average)

5. If the control current does not fluctuate, check the oxygen sensor. Refer to DIAGNOSIS AND TESTING PROCEDURES.

CAUTION: During CO adjustment:
Do not push down on the wrench while adjusting.
Do not accelerate the engine while the wrench is inserted in the CO adjusting screw.
Remove the wrench after each adjustment and briefly raise the engine speed before reading the control current on the multimeter.

6. Observe the CO content, checking value is:

0.3% to 1.2%

IDLE SPEED

1. Check the idle stabilizer valve duty cycle and coresponding idle rpm, checking values are:

26% to 30%
23° to 27° (using a dwell meter)
800 to 900 rpm

2. If the idle stabilizer valve duty cycle is OK continue to FINAL CHECK.
3. If adjustment is needed, adjust the idle stabilizer valve duty cycle by adjusting the idle air bypass screw until proper duty cycle is achieved, adjusting values are:

29% ± 1%
26° ± 1° (using a dwell meter)
850 ± 50 rpm

FINAL CHECK

1. Briefly accelerate the engine to heat the oxygen sensor.
2. Allow the engine to idle a few seconds to stabilize readings.
3. Quickly observe and record the basic engine settings.
4. If after completing the entire TEST AND ADJUSTMENT PROCEDURE, all engine settings were within specifications and no adjustments were needed, idle readings should be:

Ignition timing: 4° to 8° BTDC
Differential pressure regulator current: 4 to 16 mA
CO content: 0.3% to 1.2%
Idle stabilizer valve duty cycle: 26% to 30%
Idle stabilizer valve duty cycle: 23° to 27° (using a dwell meter)
Idle speed: 800 to 900 rpm

5. If adjustments have been made, or the engine is being set to specifications, idle readings should be:

Ignition timing: 6° ± 1° BTDC
Differential pressure regulator current: 10 ± 1 mA
CO content: 0.75% ± 0.45%
Idle stabilizer valve duty cycle: 29% ± 1%
Idle stabilizer valve duty cycle: 26° ± 1° (using a dwell meter)
Idle speed: 850 ± 50 rpm

6. If engine settings have changed after making adjustments, repeat the entire TEST AND ADJUSTMENT PROCEDURE described above (making small adjustments as necessary) until readings stay within specifications.
7. If specifications cannot be reached, a faulty component may exist and further testing is needed. Refer to DIAGNOSIS AND TESTING PROCEDURES.
8. Turn ignition switch "OFF".
9. Remove test equipment.
10. Reconnect any hoses that were disconnected during testing, reinstall cap on the CO tap tube.
11. Install a new tamper proof plug for the CO adjustment screw in the air flow sensor housing (if removed).