DESCRIPTION
The spark plug switching control system is designed to change the ignition system from 2-plug ignition to 1-plug ignition during heavy load driving in order to reduce engine noise. On automatic transmission vehicles, the system also functions to advance ignition timing by a specified value during 1-plug ignition.
On 1986 1/2 Pickup, ignition timing is controlled corresponding to engine operating conditions by the ECCS control unit. Optimum timing for all engine conditions has been programmed into the ECCS control unit.
Signals used to determine ignition timing are cylinder head temperature, throttle valve switch, engine RPM, engine load, engine crank angle, etc. The signal from the ECCS control unit is sent to the power transistor of the ignition coil to control the ignition timing. Detonation sensor monitors knocking condition and transmits the signal to the ECCS. After receiving the signal, the control unit retards ignition timing to avoid excessive knocking.
| Engine Operating Condition | Spark Control | Spark Timing | |
|---|---|---|---|
| Stanza & 200SX | |||
| Cranking (1) | 2-plugs | Normal | |
| Light Load (1) | 2-plugs | Normal | |
| Heavy Load (1) | 1-plug | (2) | |
| Any (3) | 2-plugs | Normal | |
| 1986 Pickup | |||
| Any (4) | 2-plugs | Any | |
| (5) (6) | 2-plugs | Any | |
| (5) (7) (8) | 2-plugs | Below 2400 | |
| (5) (7) (8) | 1-plug | Above 2400 | |
| (5) (7) (9) | 1-plug | Any | |
| 1986 1/2 Pickup | |||
| Normal | 2-plugs | Normal | |
| Heavy Load | 1-plug | Advanced (4°) | |
| (1) Above 59°F (15°C). (2) Advanced (A/T), Normal (M/T). (3) Below 59°F (15°C). (4) Neutral clutch inhibitor switch on. (5) Neutral clutch inhibitor switch off. (6) Vacuum switch off. (7) Vacuum switch on. (8) Below 158°F (70°C). (9) Above 158°F (70°C). | |||
| (1) | Above 59°F (15°C). |
| (2) | Advanced (A/T), Normal (M/T). |
| (3) | Below 59°F (15°C). |
| (4) | Neutral clutch inhibitor switch on. |
| (5) | Neutral clutch inhibitor switch off. |
| (6) | Vacuum switch off. |
| (7) | Vacuum switch on. |
| (8) | Below 158°F (70°C). |
| (9) | Above 158°F (70°C). |
IGNITION CONTROL (STANZA & 200SX)
WATER TEMPERATURE SENSOR
The water temperature sensor, built into the water outlet, monitors changes in coolant temperature and transmits a signal to the control unit. The temperature sensing unit employs a thermistor which is sensitive to the change in temperature. Electrical resistance of the thermistor decreases in response to temperature rise.
1986 1/2 Pickup
The crank angle sensor detects engine RPM and crank angle. It sends a signal to control unit. Sensor is built into the distributor.
Signal rotor plate has 360 slits at 1° intervals on outside edge. It also has 4 slits at 90° intervals. These slits are used to detect crank angle (piston position). The teeth are used to provide the 1° signal that is necessary to control engine RPM and ignition timing.
AIRFLOW METER
The airflow meter measures the quantity of intake air, and sends a signal to the control unit. The control unit controls spark switching.
The ignition coil has a built-in power transistor. The signal from the control unit is amplified by the power transistor. This signal is used to connect and disconnect the ignition coil's primary current to generate high voltage across the secondary coil, creating spark at spark plug.
THROTTLE VALVE SWITCH
The throttle valve switch is attached to the throttle chamber and actuates in response to accelerator pedal movement. This switch has idle contact and full throttle contact. The idle contact closes when the throttle valve is positioned at idle and opens when it is at any other position.
Check resistance values between power transistor terminal, body ground and ignition coil minus terminal. (Scheme 9) If no good, replace power transistor.
Checking Power Transistor Resistances. Scheme 9
1986 1/2 Pickup (Z24i Engine)
- Check power source. Turn ignition switch to the "ON" position. Check voltage between terminal No. 1 of power transistor harness connector and ground. Battery voltage should be present. If so, go to next step. If not, check harness continuity between battery and power transistor (exhaust side), "G" fusible link, and ignition switch.
- Check output signal. Start engine, and warm up to operating temperature. Check voltage between terminal No. 2 of power transistor harness connector and ground when depressing accelerator pedal fully and suddenly. Output voltage should drop to zero volts. If okay, go to step 4). If not go to next step.
- Check ECU. Start engine. Check voltage between terminal No. 14 of ECU 20-pin connector and ground, depressing accelerator pedal fully. Output voltage should drop to zero volts. Check harness continuity between ECU and power transistor. Disconnect 20-pin connector from ECU. Check resistance between terminals No. 2 and 4. Resistance should be zero ohms.
- Check ground circuit. Stop engine. Disconnect power transistor harness connector. Check resistance between terminal No. 3 and ground. Resistance should be zero. If not, check harness continuity as in step 3), engine ground, and power transistor ground. If resistance was okay, check power transistor. If not okay, replace unit.
1986 Pickup (Z24 engine)
- Disconnect vacuum hose from vacuum switch for spark plug switching control and connect a vacuum pump. On Federal models, except for Cab and Chassis model, connect ohmmeter leads between terminal B and body ground. With more than 3.15 in. Hg of vacuum applied, resistance should be zero. With less than 3.15 in. Hg of vacuum applied, resistance should be infinite. If test is not okay, check harness, ignition control unit and vacuum switch.
- For models others than ones mentioned in step 1), connect voltmeter between terminal B and body ground. With ignition on, pointer should deflect.