ASE Fuel Systems & Emissions Control

Question 1

What is the stoichiometric air-fuel ratio for a gasoline engine?

Accepted Answer

14.7:1

Answer

12.5:1

Answer

16.1:1

Answer

10.5:1

Question 2

What is the primary purpose of the EVAP (Evaporative Emission Control) system?

Accepted Answer

Prevent fuel vapors from escaping into the atmosphere

Answer

Recirculate exhaust gases back into the engine intake

Answer

Control fuel pressure at the injector rail

Answer

Filter contaminants from the fuel before delivery

Question 3

Which sensor provides the primary feedback signal to the ECM for closed-loop fuel control?

Accepted Answer

Oxygen (O2) sensor

Answer

Mass Airflow (MAF) sensor

Answer

Throttle Position Sensor (TPS)

Answer

Engine Coolant Temperature (ECT) sensor

Question 4

What does a MAF (Mass Airflow) sensor measure?

Accepted Answer

The mass of air entering the engine per unit of time

Answer

The temperature of intake air only

Answer

The pressure differential across the air filter

Answer

The volume of exhaust gases leaving the engine

Question 5

What is the primary purpose of the EGR (Exhaust Gas Recirculation) system?

Accepted Answer

Reduce NOx emissions by lowering peak combustion temperatures

Answer

Increase fuel efficiency by re-burning exhaust gases completely

Answer

Prevent carbon buildup on intake valves in port-injected engines

Answer

Filter particulate matter from exhaust gases before emission

Question 6

What component stores fuel vapors in the EVAP system between purge events?

Accepted Answer

Activated charcoal canister

Answer

Fuel pressure regulator

Answer

PCV valve and crankcase assembly

Answer

Catalytic converter substrate

Question 7

A port fuel injector is best described as a:

Accepted Answer

Electronically controlled solenoid valve that meters fuel

Answer

Mechanically operated diaphragm pump driven by cam lobe

Answer

Vacuum-controlled needle valve regulated by manifold pressure

Answer

Spring-loaded check valve opened by fuel pressure alone