ASVAB Automotive Information 4 — Questions and Answers
Question 1: What is the purpose of a differential in a vehicle's drivetrain?
- To increase engine torque output
- To allow drive wheels to rotate at different speeds when turning (Correct answer)
- To engage and disengage the drivetrain from the engine
- To convert engine torque to electrical power
Correct answer: To allow drive wheels to rotate at different speeds when turning
The differential allows the outer wheel to rotate faster than the inner wheel during a turn, preventing tire scrub and allowing smooth cornering.
Question 2: What is 'detonation' (engine knock) in a gasoline engine?
- Normal combustion where the spark plug ignites the mixture
- Uncontrolled premature ignition of the air-fuel mixture before the spark plug fires (Correct answer)
- The sound of a worn timing chain
- Exhaust backfiring through the intake
Correct answer: Uncontrolled premature ignition of the air-fuel mixture before the spark plug fires
Detonation (knock) occurs when the compressed air-fuel mixture ignites spontaneously before the spark plug fires, creating a characteristic knocking sound and potentially damaging the engine.
Question 3: What is the primary function of anti-lock brakes (ABS)?
- To shorten stopping distance on all surfaces
- To prevent wheel lockup during hard braking, maintaining steering control (Correct answer)
- To automatically apply brakes on steep hills
- To reduce brake pad wear during normal driving
Correct answer: To prevent wheel lockup during hard braking, maintaining steering control
ABS prevents wheels from locking up during emergency braking by rapidly modulating brake pressure, allowing the driver to maintain steering control.
Question 4: Which component seals the combustion chamber between the cylinder block and cylinder head?
- Valve stem seal
- Head gasket (Correct answer)
- Piston ring
- Crankshaft seal
Correct answer: Head gasket
The head gasket seals the joint between the engine block and cylinder head, preventing combustion gases, coolant, and oil from mixing or leaking externally.
Question 5: What does a vehicle's mass airflow (MAF) sensor measure?
- Exhaust gas temperature
- The amount of air entering the engine to help calculate fuel delivery (Correct answer)
- Intake manifold vacuum pressure
- Engine oil temperature
Correct answer: The amount of air entering the engine to help calculate fuel delivery
The MAF sensor measures the mass of air entering the engine, and the ECU uses this data to calculate the correct fuel injection quantity for the proper air-fuel ratio.
Question 6: If a car's temperature gauge rises to the red zone while driving, what should the driver do first?
- Turn on the air conditioning to cool the engine
- Safely pull over and shut off the engine to prevent damage (Correct answer)
- Continue driving slowly to a service station
- Add cold water directly to the hot radiator
Correct answer: Safely pull over and shut off the engine to prevent damage
An overheating engine can suffer severe damage quickly; the correct response is to safely stop and shut off the engine to allow it to cool before investigating the cause.
Question 7: What type of suspension system uses a single large pivot point per wheel, with no upper control arm?
- Double wishbone suspension
- MacPherson strut suspension (Correct answer)
- Multi-link suspension
- Solid axle suspension
Correct answer: MacPherson strut suspension
MacPherson strut suspension combines the shock absorber and strut into a single unit attached to the steering knuckle, requiring only a lower control arm and no upper control arm.
ASVAB Automotive Information 4
What is the purpose of a differential in a vehicle's drivetrain?