EMISSION APPLICATIONS
Control of exhaust emission is accomplished by combination of engine modifications and special system components. Component usage varies according to model, engine, states, and emissions cycle application.
Note. There are 2 light duty truck emission control standards classifications: Light Duty and Heavy Duty. Light Duty refers to vehicles up through 8500 lbs. GVW; Heavy Duty refers to vehicles over 8500 lbs. GVW.
THERMOSTATIC AIR CLEANER (TAC)
The TAC system provides heated air to carburetor (from stove on exhaust manifold) in combination with underhood air. The TAC maintains constant intake air temperature during engine warmup for more efficient combustion and emission control.
AIR INJECTION
The air injection system consists of air pump, air control valve, check valves, injection tubes and various air distribution lines. Injection of fresh air adjacent to exhaust valves creates an afterburn effect, which results in lower emission levels.
ASPIRATOR AIR SYSTEM
The aspirator air system is used to reduce carbon monoxide and hydrocarbon emissions by drawing fresh air from air cleaner, and allowing it to mix with exhaust gases. The system consists of aspirator air valve and connecting tubes to air cleaner and exhaust manifold.
EXHAUST GAS RECIRCULATION (EGR)
The EGR system allows a predetermined amount of hot exhaust gas to recirculate and dilute air/fuel mixture. This aids combustion and reduces NOx emissions.
ELECTRONIC FUEL CONTROL & ELECTRONIC SPARK ADVANCE
The Electronic Fuel Control (EFC) and Electronic Spark Advance (ESA) system is an electronically controlled system that closely manages air/fuel ratio and ignition timing. The Electronic Fuel Control (EFC) and Electronic Spark Advance (ESA) is the heart of the system.
This computer provides the capability of igniting a lean air/fuel mixture according to different modes of engine operation; plus, during closed loop operation, the computer maintains air/fuel mixture close to the ideal ratio of 14.7:1. For additional information, see appropriate article in the COMPUTERIZED ENGINE CONTROLS section.
ELECTRIC ASSIST CHOKE
The electric assist choke system is designed to give faster choke openings at temperatures above 60°F (16°C) and slower choke openings below 60°F (16°C).
CATALYTIC CONVERTER
The exhaust catalytic converter system brings about combustion-type reaction to further consume unburned elements in engine exhaust. Catalytic converter is located in exhaust system ahead of muffler. Vehicles equipped with catalytic converters must use unleaded fuel only.
POSITIVE CRANKCASE VENTILATION (PCV)
The PCV system is used on all vehicles to eliminate fumes and vapors from crankcase. The PCV system directs fumes and vapors back through combustion chamber to be burned.
EVAPORATION CONTROL SYSTEM
Dual canister evaporation control system is used on all vehicles. The system routes fuel vapors from fuel tank through filter canisters to engine for burning. This closed system prevents vapors from venting to the atmosphere.
PULSE AIR FEEDER SYSTEM (2.6L)
Pulse air feeder system supplies secondary air into exhaust system between front and rear catalytic converters. This promotes oxidation of exhaust emissions in the rear catalytic converter.
This system consists of main reed valve and sub reed valve. Main reed valve is controlled by diaphragm which is activated by pressure pulses from within the crankcase. Sub reed valve is activated by pulsation in exhaust system between front and rear converters.
JET AIR VOLUME CONTROL SYSTEM (2.6L)
The system consists of jet air control valve (which is an integral part of the carburetor) and thermo valve which is controlled by coolant temperature.
Purpose of this system is to help decrease HC and CO emissions during engine warm-up while choke is operating.
TESTING
Note. Testing information not available.