ASVAB Automotive Information 3 — Questions and Answers
Question 1: What does 'overhead cam' (OHC) mean in engine design?
- The camshaft is located in the engine block below the cylinders
- The camshaft is located in the cylinder head above the valves (Correct answer)
- The camshaft is driven by a hydraulic pump
- The camshaft controls fuel injection only
Correct answer: The camshaft is located in the cylinder head above the valves
In an overhead cam engine, the camshaft is mounted in the cylinder head directly above the valves, eliminating pushrods and allowing for higher RPM operation.
Question 2: What is the purpose of a vehicle's sway bar (stabilizer bar)?
- To increase ground clearance
- To reduce body roll during cornering by linking opposite wheels (Correct answer)
- To adjust ride height automatically
- To dampen engine vibration
Correct answer: To reduce body roll during cornering by linking opposite wheels
The sway bar connects opposite wheels through short links and reduces body roll during cornering by transferring force from the compressed side to the extended side.
Question 3: What type of oil rating system is used in the US to classify motor oil by viscosity?
- ISO ratings
- SAE ratings (Correct answer)
- API ratings
- ASTM ratings
Correct answer: SAE ratings
The Society of Automotive Engineers (SAE) viscosity rating system (e.g., 5W-30) classifies motor oil by its flow characteristics at cold and operating temperatures.
Question 4: A vehicle is pulling to one side when braking. What is the most likely cause?
- Low engine oil
- A stuck or seized brake caliper on one side (Correct answer)
- A worn timing belt
- A faulty alternator
Correct answer: A stuck or seized brake caliper on one side
A seized caliper on one side applies more braking force to that wheel than the other, causing the vehicle to pull toward the side with the stuck caliper.
Question 5: In a four-stroke engine, what occurs during the 'compression' stroke?
- Both valves open to allow exhaust to escape
- Both valves are closed while the piston moves up, compressing the air-fuel mixture (Correct answer)
- The spark plug fires and ignites the mixture
- The piston moves down while the intake valve opens
Correct answer: Both valves are closed while the piston moves up, compressing the air-fuel mixture
During the compression stroke, both intake and exhaust valves are closed and the piston moves upward, compressing the air-fuel mixture before ignition.
Question 6: What does the 'W' in a motor oil designation like 5W-30 stand for?
- Weight
- Winter (Correct answer)
- Wear
- Wet
Correct answer: Winter
The 'W' stands for Winter, indicating the oil's viscosity rating at low temperatures to ensure proper cold-weather starting and initial lubrication.
Question 7: Which sensor measures the amount of oxygen in the exhaust to help regulate the air-fuel mixture?
- MAP sensor
- O2 (oxygen) sensor (Correct answer)
- MAF sensor
- Throttle position sensor
Correct answer: O2 (oxygen) sensor
The oxygen sensor (O2 sensor) monitors oxygen content in exhaust gases and sends signals to the ECU to adjust the air-fuel ratio for optimal combustion and emissions.
ASVAB Automotive Information 3
What does 'overhead cam' (OHC) mean in engine design?