DESCRIPTION
Deceleration fuel cut-off system is used only on models with M/T. System reduces fuel consumption and HC emissions by stopping injection of fuel during deceleration. System consists of relay, vacuum valve, and by-pass hose.
OPERATION
Deceleration system relay is activated only when coolant temperature is above 113°F (45°C), relay switch is in rest position and engine speed exceeds 1400-1750 RPM. When throttle switch closes, system will operate until engine speed decreases below 1300-1475 RPM.
When system operates, flow of air is led through by-pass hose and vacuum valve instead of passing air flow sensor plate. Air flow sensor plate drops to rest position, which cuts off fuel to cylinders.
TESTING
- Disconnect wiring connector from throttle switch. Use ohmmeter to ensure there is good connection between plug on throttle switch and ground when the throttle switch is released. Reconnect wiring to switch.
- Connect Bosch Tester (KDJE 7453) to 2-pole test socket located in front of fuse box. Run engine at 875 RPM. Disconnect wiring connector from vacuum valve.
- Using voltmeter, check that there are 12 volts between connector and ground. Reconnect wiring to vacuum valve and increase engine speed to 2000 RPM. Release accelerator suddenly.
- Use hand to feel if vacuum valve is operating. Sharp reduction in engine RPM also indicates that valve is working. Check that Lambda system assumes a fixed pulse relation (60%) until system cuts out at 1300-1450 RPM.
