Cold Engine

NOTE: Engine coolant temperature must be below 140°F (60°C).

Fig 1: Ignition Timing Controls

Disconnect vacuum hose No. 8 from vacuum advance diaphragm. Connect vacuum gauge to hose. Start engine and run at idle. There should be vacuum. If there is vacuum, proceed to HOT ENGINE test.
If there is no vacuum, check for voltage at vacuum control solenoid valve in emission control box No. 1 (4P connector Blue/Black wire). If there is voltage, replace vacuum control solenoid and retest. If there is no voltage, check the following.
On man. trans. models, check thermosensor and intake air temperature sensor. Check for voltage at control box connector (Black/Yellow wire) with ignition on. There should be voltage. If there is no voltage, check wiring. Ensure Brown/Black wire between control unit and ground has continuity.
On auto. trans. models, check for voltage at control unit connector (Blue wire) with ignition on. There should be voltage. If there is no voltage, check Blue wire between control unit and ignition coil. Check speed sensor, thermosensor, intake air temperature sensor and vacuum switch C.
Check for voltage at control box connector (Black/Yellow wire) with ignition on. There should be voltage. If there is no voltage, check wiring. Ensure Brown/Black wire between control unit and ground has continuity.