| Description and Operation Introduction The engine management system of the HCS TBI engine in the Escort '91 comprises a powertrain control module and a number of other components which are either sensors or actuators. The sensors supply the powertrain control module with input signals which relate to engine operating conditions and the actuators respond to output signals from the powertrain control module. These output signals are based on the evaluated input signals which are compared with calibrated data tables or maps before the output signal is generated. The 1,3 litre HCS TBI engine meets 83 US emission regulations. To achieve this standard of emission control, the engine is equipped with a catalytic converter, pulsed secondary air injection and an evaporative emission fuel vapour management system. The sensors and actuators utilised are part of the generic family of components used on all Ford EEC IV engine management systems and their functions are described in detail in the FDS 2000 Vehicle System Test Manual (CG1591). Evaporative Emission Fuel Vapour Management The evaporative emission fuel vapour management system comprises a carbon canister and a purge valve. A combination of plastic and rubber pipes connect the carbon canister to the fuel tank and the purge valve and to the inlet manifold. When the purge valve is closed, the fuel tank is vented into the carbon canister which absorbs the fuel vapour and prevents the release of hydro‐carbons into the atmosphere. When the purge valve is activated, the carbon canister is exposed to inlet manifold vacuum and the fuel vapour deposits are drawn into the inlet manifold where they mix with the incoming air/fuel charge. The evaporative emission fuel vapour management system is controlled by the powertrain control module according to calibrated data tables. The function of the system is to reduce hydro‐carbon emissions from the fuel tank. Pulsed Secondary Air Injection The pulsed secondary air injection system allows the introduction of fresh air into the exhaust manifold which causes secondary combustion to occur. This secondary combustion reduces the time taken by the catalytic convertor to reach it's operating temperature. Powertrain Control Module The engine management system utilises a 60‐pin powertrain control module (EEC IV) which is located behind the passenger cowl side trim panel. From '95½ MY onwards, the powertrain control module is protected by a steel security cover to maintain the integrity of the passive anti‐theft system. | 
