Without BMW Tester

Fig. 10 Spark Advance Control Wiring Diagram:

The complete vacuum advance control system can only be checked with BMW tool# 12 1 460 or equivalent and BMW service test unit or BMW digital tester. There is a separate test for the vacuum advance solenoid valve (VASV), coolant temperature switch and the intake air temperature sensor. They can be tested as follows:


VACUUM ADVANCE SOLENOID VALVE:
1. Check all vacuum hoses for leaks, clogging and condition.
2. Disconnect the electrical connectors at the VASV.
3. Connect a test lamp from green-yellow wire to ground of vehicle. Turn on ignition. Test lamp should illuminate. If not, check fuse #9 (located in engine compartment, behind left front shock tower) and/or wiring for defect(s).
4. Turn off ignition.
5. Disconnect vacuum hose (at VASV) leading to the intake manifold.
6. Disconnect vacuum hose at vacuum advance unit and blow air through it. The air should flow through the VASV and exit at the connection to the intake manifold vacuum hose (not the ventilation outlet).
7. If air does not flow through VASV or if air exits at the wrong outlet, check for clogged vacuum lines and connections. If vacuum lines and connections are o.k., replace and retest with new VASV.
8. Ground the terminal on the VASV going to the ECU (terminal that the white-brown wire would be connected to).
9. Apply 12 volts to the other terminal (terminal that the green-yellow wire would be connected to ).
10. Blow air through vacuum advance hose. The air should flow through the VASV and exit at the ventilation outlet (not at the connection to the intake manifold vacuum hose).
11. If air does not flow through VASV or if air exits at the wrong outlet, check for clogged vacuum lines and connections. If vacuum lines and connections are o.k., replace and retest with new VASV.
12. Disconnect all test equipment and connect vacuum lines and electrical connectors.
13. If VASV performs without defects, check wiring to vacuum advance control unit (located forward of left front shock tower).
14. If there is still a problem, defect may exist in the vacuum advance control unit, coolant temperature switch or air intake temperature sensor. Vacuum advance control unit can only be tested with BMW tool# 12 1 460 or equivalent and BMW service test unit or BMW digital tester (see testing "WITH BMW TESTER").


COOLANT TEMPERATURE SWITCH:
1. If coolant temperature switch (located in front of engine, top of thermostat housing) is checked below 45°C (113°F), pull off connector at idle control unit (located in glove box above L-jetronic control unit).
2. Disconnect white wire connector at temperature switch and connect an ohmmeter between switch terminal (where white wire would connect) and ground.
3. Ohmmeter should read as follows:
coolant temperature above 45°C (113°F) closed circuit (low or no resistance)
coolant temperature below 30°C (86°F) open circuit (infinite resistance)
4. If measured value is different, replace and retest with new switch. Disconnect ohmmeter and reconnect connector at switch and idle speed control unit.


INTAKE AIR TEMPERATURE SENSOR:
1. The intake air temperature sensor is located below air cleaner in left front corner of engine compartment.
2. Disconnect air temperature sensor connector. Measure the resistance between the terminals. Ohm reading should be:
at 10 - 38°C (50 - 100°F) 950 ± 20 ohms
3. If measured value is different, replace and retest with new sensor. Reconnect air temperature sensor connector.