Without Volkswagen Tester VAG 1551

The air/fuel mixture is controlled by the CIS-E Motronic control unit. The purpose of the idle mixture adjustment is to assure that the oxygen sensor system is operating near the middle of its control range.
Idle checks or adjustments will be valid only after the CIS-E Motronic fault memory is clear and the ignition timing is correct. Any faults stored in memory must be corrected. Refer to COMPUTERS AND CONTROL SYSTEMS/TESTING AND INSPECTION.
Making these checks and adjustments together is very important in order to obtain satisfactory driveablity characteristics and emission levels.

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/TESTING AND INSPECTION.
5. Fault memory must be clear of stored faults. If any are found, they must be corrected and then fault memory erased before proceeding. Refer to COMPUTERS AND CONTROL SYSTEMS/TESTING AND INSPECTION.
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. Refer to COMPUTERS AND CONTROL SYSTEMS/TESTING AND INSPECTION.
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 parking brake.
2. Turn the ignition switch "OFF".

Checking Motronic Ignition:

3. Connect VAG 1367 engine tester using VAG 1367/8 inductive pickup, or an equivalent engine analyzer with strobe timing light and tachometer.

CO Tester Hookup:

4. 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. Use 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. a. Disconnect the 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 remain in hose #2.

Carbon Canister Frequency Valve:

b. Disconnected the vacuum hose to the frequency valve.

7. Ensure that ignition switch is turned "OFF".
8. Disconnect the harness connector from differential pressure regulator.

NOTE: On the PASSAT, access to the differential pressure regulator is limited. Trace the wiring harness from the differential pressure regulator up to the harness connector located on the right shock tower. The connector is positioned in a small holder. Use this connector for test equipment hook-up instead of the connector at the differential pressure regulator.

Checking Differential Pressure Regulator:

9. Connect test adaptor VAG 1315A/1 (or equivalent) between differential pressure regulator and harness connector.
10. Switch a suitable multimeter such as the Fluke 83 multimeter to 200 mA range.
11. Connect multimeter to test adaptor VAG 1315A/1 using jumper wires from VW 1594 adaptor kit.
12. Turn the ignition switch "ON".
13. Control current must be displayed as positive polarity (90 to 110 mA). If negative polarity is displayed, reverse the multimeter test leads.
14. Start the engine and let it idle.

Ignition Timing Mark:

IGNITION TIMING

1. Check the ignition timing, checking value is:

4° to 8° BTDC

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

6° ± 1° BTDC (timing indicators should be aligned).

4. Tighten the distributor bolts to specification.

IDLE SPEED

Idle Air Bypass Screw 16v:

1. Check the idle air bypass screw, it should be in the closed or bottomed position, it is not used for idle adjustment.
2. Idle speed rpm's can not be adjusted.

CO CONTENT

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

800 to 1000 rpm

CO Adjustment Motronic:

3. Adjust the differential pressure regulator control current using a long 3mm hex wrench in CO adjusting screw, adjusting value is:

2.5 ± 2.5 mA (must fluctuate)

4. If the control current does not fluctuate, check the oxygen sensor and oxygen sensor control. Refer to COMPUTERS AND CONTROL SYSTEMS/TESTING AND INSPECTION.

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.

5. Observe the CO content. CO volume must be:

0.2% to 1.2%

6. Turn the ignition switch "OFF".
7. Remove the test equipment.
8. Reinstall any hoses that were disconnected during testing and reinstall the cap on the CO tap tube.
9. Install a new tamper proof plug for the CO adjustment screw in the air flow sensor housing.