Reference Manual

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Chapter 10: Emissions Equipment: Introduction

Long before the G-body's time, emissions control consisted of keeping valve seals good so you wouldn't burn all your oil away.  Perhaps the first step towards reducing emissions, the PCV (Positive Crankcase Ventilation) system was implemented in the 1960s.   The late 1960s and early 1970s saw the introduction of EGR valves and catalytic converters and by 1975, converters were a federally-required piece of equipment on all gasoline passenger cars.

In the day of the G-body, emissions control had "advanced" to the level of using an engine-driven air pump which supplied fresh air to the exhaust stream or catalytic converter based on certain engine conditions.  The environment (coolant temperature, barometric pressure, speed, etc) was sensed by an ECM (Engine Control Module) and the smog system's switching valve was controlled electronically.  Further, thermostatically-controlled air cleaners and exhaust valves were used to reduce vehicle emissions even further.