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GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide



In its normal operation, the internal combustion engine releases several compounds into the atmosphere. Since most of these compounds are harmful to our health if inhaled or ingested for long periods (and in sufficient quantity), the Federal Government has placed a limit on the quantities of the three main groups of compounds: unburned hydrocarbons (HC); carbon monoxide (CO); and oxides of nitrogen (NOx).

The emissions systems covered in this section are designed to regulate the output of these fumes by your vehicle's engine and fuel system. Three areas of the automobile are covered, each with its own anti-pollution system or systems; the engine crankcase, which emits unburned hydrocarbons in the form of oil and fuel vapors; the fuel storage system (fuel tank and carburetor), which also emits unburned hydrocarbons in the form of evaporated gasoline; and the engine exhaust. Exhaust emissions comprise the greatest quantity of auto emissions, in the forms of unburned hydrocarbons, carbon monoxide, and oxides of nitrogen. Because of this, there are more pollution devices on your vehicle dealing with exhaust emissions than there are dealing with the other two emission types.

Exhaust emission controls comprise the largest body of emission controls installed on your vehicle. Included in this category are:

Thermostatic Air Cleaner (THERMAC)
Air Injection Reactor System (A.I.R., 1975-80)
Air Management System (1981 and later)
Early Fuel Evaporation system (EFE)
Exhaust Gas Recirculation
Controlled Combustion System (CCS)
Computer Controlled Catalytic Converter system (C-4)
Computer Command Control (CCC)
Mixture Control Solenoid (M/C)
Throttle Position Sensor (TPS)
Idle Speed Control (ISC)
Electronic Spark Timing (EST)
Electronic Spark Control (ESC)
Transmission Converter Clutch (TCC)
Catalytic Converter and the Oxygen Sensor system

A brief description of each system and any applicable service procedures follows.