Emissions Control Systems Review

These flashcards cover key terms and concepts related to emissions control systems, pollutants, and diagnostic processes.

EGR

Exhaust Gas Recirculation

EVAP

Evaporative Emissions Control System

AIR

Air Injection Reaction

PCV

Positive Crankcase Ventilation

HC

Hydrocarbons

CO

Carbon Monoxide

NOx

Nitrogen Oxides

TWC

Three-Way Catalytic Converter

DPFE

Delta Pressure Feedback EGR (sensor)

DTC

Diagnostic Trouble Code

What are the three main pollution gases created by combustion that we try to reduce?

Hydrocarbons (HC), Carbon Monoxide (CO), Nitrogen Oxides (NOx)

Which state was the first to implement emissions laws?

California

What is the main job of the EGR system?

To reduce NOx emissions by recirculating exhaust gases to lower combustion temperatures.

What components were added to the basic EVAP system for OBD-II?

Purge valve, vent valve, fuel tank pressure sensor.

How can the PCM determine proper EGR valve operation?

By monitoring MAP sensor readings, DPFE sensor feedback, and engine performance.

What is the purpose of the PCV valve?

To vent crankcase gases back into the intake manifold to reduce emissions and oil contamination.

What emissions gas does the EVAP system control?

Hydrocarbons (HC)

What temperature does a converter need to become efficient?

Around 500 to 600°F (260 to 315°C)

What is a vapor canister used for?

To store fuel vapors from the fuel tank until they can be purged and burned in the engine.

What tool is typically most useful when locating leaks in the EVAP system?

Smoke machine (EVAP smoke tester)

Which emission system sends extra oxygen to the converter?

AIR system (Secondary Air Injection)

At what temperature does NOx form in the combustion chamber?

Above 2500°F (1370°C)

How does the PCM determine correct catalytic converter operation?

By comparing pre- and post-O2 sensor signals.

Which gas is primarily responsible for greenhouse gases?

Carbon Dioxide (CO₂) – results from complete combustion.

Which combustion gas is odorless, colorless, and deadly?

Carbon Monoxide (CO)

What is the most likely problem when a gas pump shuts off while fueling?

Restriction in the EVAP vent system or clogged vent valve/canister.

What should happen to the exhaust temperature as it passes through a functioning converter?

It should increase as the catalytic converter generates heat.

What is the difference between pre-O2 and post-O2 sensors on a proper operating converter?

Pre-O2 should fluctuate; post-O2 should be stable (flatline).

During what type of driving should the EGR valve be open?

Cruising or part-throttle driving.

What is the name of the emissions sticker located in the engine compartment?

Vehicle Emissions Control Information (VECI) label.

What system was able to be eliminated by VVT?

EGR system - in some engines, Variable Valve Timing controls internal EGR.

What is located inside of a vapor canister that absorbs fuel vapors?

Activated charcoal.

What tools can be used to test a converter?

Infrared thermometer, scan tool (O2 sensor readings), 5-gas analyzer.

How many drive cycles does it typically take for the Check Engine Light to come on after a problem?

Usually 2 consecutive drive cycles.

Where are common areas for leaks to occur in the EVAP system?

Gas cap, vent valve, purge valve, canister hoses, fuel tank pressure sensor.