Emission_Control_Diagnosis_Flashcards
(21 cards)
Which emission system controls fuel vapor from the tank?
EVAP system.
T/F: The PCM can detect EVAP leaks as small as 0.5 mm.
True.
How can you tell if a catalytic converter is working? (Hint: Temperature check)
The outlet temperature should be 10%–30% hotter than the inlet.
What engine condition can damage a catalytic converter?
A misfire or excessively rich/lean mixture.
What causes excessive hydrocarbons in the exhaust?
Unburned fuel due to ignition issues or improper air/fuel ratio.
T/F: Excessive NOx is caused by low combustion temperatures.
False – It’s caused by high combustion temperatures.
What does a white spark plug insulator indicate?
A lean air/fuel mixture.
What does dry black carbon on spark plugs indicate?
A rich air/fuel mixture.
How can you check if the catalytic converter substrate is broken? (Hint: Rubber mallet)
Lightly tap it and listen for rattles.
What are the three primary pollutants emitted by vehicles?
Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx).
What emission control system prevents fuel vapor release from the tank?
EVAP (Evaporative Emission Control System).
T/F: The PCM on OBD2 vehicles can detect EVAP leaks as small as 0.5 mm.
True.
When performing a smoke test, what component must be closed for a proper test? (Hint: Normally open)
The vent solenoid.
What sensors are used to evaluate catalytic converter efficiency?
Upstream (pre-cat) and downstream (post-cat) O2 sensors.
What should the outlet temperature of a working cat be relative to the inlet? (Hint: % range)
10% to 30% hotter.
What engine issue can permanently damage a catalytic converter?
A misfire or overly rich/lean fuel mixture.
T/F: A rattle when tapping the catalytic converter housing may indicate a broken substrate.
True.
What are some causes of high hydrocarbon emissions?
Ignition faults, rich or lean mixtures, low compression, or a faulty catalytic converter.
What spark plug color indicates a lean fuel mixture?
White porcelain.
What causes excessive CO emissions? (Hint: Too much fuel or not enough air)
Rich mixture due to restricted air, faulty injector, high fuel pressure, or EFI sensor fault.
What are common causes of excessive NOx emissions?
Inoperative EGR, combustion chamber carbon buildup, or high coolant temps.
