Honda Civic Emission Systems: egr, evap and pcv

Honda Civic 1992-1995 EG

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

EGR system reduces oxides of nitrogen (NOX) emissions by recirculating exhaust gases through EGR valve into intake manifold and back to combustion chambers. System is composed of EGR valve, Constant Vacuum Control (CVC) valve and EGR control solenoid valve. EGR control solenoid valve is controlled by ECM, which analyzes input signals from EGR valve lift sensor and various sensors to provide optimum EGR flow. EGR flow is cut when combustion gas temperatures are low (when the engine emits a relatively low NOX emission) to ensure good colddriveability.

EGR Valve

When opened, EGR valve circulates exhaust gas through intake manifold and back into combustion chamber to be reburned, resulting in reduced combustion chamber temperature. Lower temperature reduces oxides of nitrogen (NOX) and helps to control spark knock.

EGR Control Solenoid Valve

When ECM determines it is necessary to recirculate exhaust gases, it grounds EGR control solenoid valve, regulating vacuum controlling EGR valve. By regulating vacuum to EGR valve, EGR flow is adjusted for optimum control of NOX emission.

Exhaust Gas Recirculation Valve Lift Sensor

The EGR valve lift sensor detects EGR valve lift and sends information to ECM. The ECM uses this information, along with other sensor inputs, to determine regulation of EGR control solenoid valve.

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EVAPORATIVE EMISSION SYSTEM (EVAP)

Evaporative emission system minimizes fuel vapor escaping into atmosphere. For emission control applications and components used for each model and engine.

Charcoal Canister

Charcoal canister temporarily stores fuel vapor until it can be purged, drawn into engine and burned in combustion chamber.

Fuel Tank Vapor Control System

Fuel tank vapor control system consists of a fuel cut-off valve, liquid/vapor separator, a 2-way valve and fuel filler cap. All fuel vapor inside fuel tank is directed to charcoal canister through fuel cut-off valve and liquid/vapor separator.

Fuel cut-off valve and liquid/vapor separator prohibit liquid fuel from entering 2-way valve. When fuel vapor pressure in fuel tank is greater than set value of 2-way valve, valve opens and regulates flow of fuel vapor into canister. The 2-way valve regulates both pressure and vacuum in tank. The filler cap contains a relief valve to prevent excessive pressure or vacuum build-up.

Vapor Purge Control System

The vapor purge control system controls when charcoal canister is to be purged. Canister purging is accomplished when ECM activates purge control cut-off solenoid valve, allowing fresh air to be drawn through bottom of charcoal canister and into a port on throttle body.

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POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM

The Positive Crankcase Ventilation (PCV) system is designed to prevent blow-by gases (in engine crankcase) from escaping into atmosphere. The PCV valve contains a spring-loaded plunger. When engine starts, plunger in PCV valve is lifted in proportion to intake manifold vacuum, and blow-by gas is drawn directly into intake manifold.



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Honda Civic 1992-1995 EG

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