Several systems are used to control vehicle emissions. System usage depends on model, engine and transmission combination. Specially calibrated fuel and ignition systems 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 content of 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 into 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 content of exhaust gases. This gas reduction is achieved by injection of clean air into the exhaust gases.
Unlike the conventional thermactor system, with MTA clean air can be injected into exhaust manifolds or catalytic converter. Operation of control valves determines the clean air injection location. During certain operating conditions the air supply may be diverted 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.
Thermactor II/Pulse Air
The Pulse Air or Thermactor II system does not use an air pump. Instead the natural exhaust pulses in the exhaust system are used to pull clean air into the exhaust manifold and/or catalyst through pulse air valves.
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. In some applications, air is injected into the catalyst by a secondary air source, pulse air or thermactor air injection.
ELECTRONIC ENGINE CONTROL (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.
On the Aerostar, the ECA unit is located in the left side dash panel of the passenger compartment. On Ranger and Bronco II the ECA unit is located on right side of dash behind kick panel. On F150/350 and Bronco series, the ECA unit is located behind kick panel on left side of dash. On E150/350 series ECA unit is located on right side dash panel under heater blower motor.
OTHER EMISSION SYSTEMS
For additional information on description, operation, testing and adjusting other exhaust emission systems, refer appropriate articles in this section.