EMISSION APPLICATIONS
Several systems are used to control engine emissions from pollutants. System usage depends on model, engine and transmission combination. Each system is designed to control a particular vehicle emission. Specially calibrated carburetors, distributors and modified combustion chambers are used with these systems.
Note. There are 2 light duty truck emission standards classifications: Light Duty and Heavy Duty Emissions. Light Duty refers to vehicles up through 8500 lbs. GVW; Heavy Duty refers to vehicles over 8500 lbs. GVW.
Conventional Thermactor Air
The Conventional Thermactor Air injection system reduces the hydrocarbons and carbon monoxide entering the exhaust gases. This gas reduction is achieved by injecting clean air into the exhaust gases.
Clean air is injected into the exhaust manifolds. During system operation, some of the air is dumped to the atmosphere to prevent excessive exhaust heat. Operation of a belt driven vane type air pump provides the air supply. Air control valves, check valves and various air distribution lines provide air injection.
Managed Thermactor Air
The Managed Thermactor Air (MTA) air injection system reduces the hydrocarbons and carbon monoxide entering the exhaust gases. This gas reduction is achieved by injection of clean air into the exhaust gases.
Clean air can be injected into exhaust manifolds or catalytic converter. Operation of control valves determines the clean air injection location. During system operation, the air supply may be delivered to the atmosphere. Operation of a belt driven vane type air pump provides the air supply. Air control valves, check valves and various air distribution lines provide air injection.
CATALYTIC CONVERTER
Catalytic converter is used for reducing exhaust emissions. Catalytic converter is mounted in-line with exhaust system. Chemical reaction with exhaust gases and catalytic internal components reduce the air pollutants of exhaust gases.
DECEL THROTTLE CONTROL
Throttle plates must be controlled during deceleration to provide improved emission control. Throttle plates must be held slightly open during deceleration. Throttle kicker, dashpot or solepot is used for throttle plate control depending on application.
ELECTRONIC ENGINE CONTROL SYSTEM (EEC-IV)
The EEC-IV system monitors engine operation to provide proper engine emission and fuel economy. EEC-IV system operation is controlled by the Electronic Control Assembly (ECA).
The ECA receives information from several sensors and electronic devices. Output signals are then generated to control engine operation. Calibration module for EEC-IV systems is mounted inside ECA.
Engine operation is controlled in 3 areas by the EEC-IV system. These areas are air/fuel mixture, ignition, and emission control. This system provides self-diagnostic capabilities for engine operation.
EVAPORATIVE EMISSION CONTROL
This system is used to keep fuel vapors from escaping into the atmosphere. Fuel vapors from the carburetor or fuel tank are stored in the carbon canister when engine is not in operation.
Engine operation then allows fuel vapors to purge from system and enter the engine. This clears the carbon canister allowing acceptance of fuel vapors during next engine shut down period.
EXHAUST GAS RECIRCULATION
The Exhaust Gas Recirculation (EGR) system introduces metered amounts of exhaust gas into engine's combustion chambers. This exhaust gas injection lowers peak combustion chamber temperatures and reduces NOx formation.
Injection of the exhaust gas is provided by a vacuum-operated EGR valve. On engines equipped with the EEC-IV system, the control assembly signals solenoids determining vacuum supply to the EGR valve.
Air By-Pass Valve
The air by-pass valve maintains engine idle speed on fuel injected engines. Operation of the air by-pass valve is controlled by the EEC-IV module. Operating of the valve allows air to pass around the throttle plates. Cold fast idle, idle load correction, dashpot and temperature idle boost are controlled by the air by-pass valve.
Idle Speed Control
The Idle Speed Control (ISC) is used on the 2.0L Ranger to control engine idle RPM. Operation of the ISC is controlled by an Idle Speed Module.
POSITIVE CRANKCASE VENTILATION (PCV)
The PCV system removes engine crankcase vapors which result from normal engine combustion. The vapors are drawn through a metered PCV valve and routed back into the intake manifold. Here the vapors are reburned in the combustion chamber.
THERMOSTATIC AIR CLEANER
Thermostatic controlled air cleaner is used for engine emission control. Airflow into air cleaner inlet is controlled by a door mounted in the intake duct. The door operation is controlled by a vacuum motor. Vacuum operation is controlled by various sensors, switches and vacuum controls.
Primary operation of air duct system is to provide maximum warm air during engine warm up period and controlling air intake temperature. Warm air is provided by the heat shroud installed on exhaust manifold.
ELECTRIC CHOKE
Voltage is supplied to the heating element. Heating element provides heat to thermostatic coil. Operation of thermostatic coil regulates the choke plate movement.
On Ranger and Bronco II models, voltage is provided by a relay operated from the alternator stator. On all others models voltage is provided through an oil pressure switch.