ASVAB Automotive Information 5 — Questions and Answers
Question 1: What is the purpose of a vehicle's catalytic converter?
- To increase exhaust flow and engine power
- To convert harmful exhaust pollutants (HC, CO, NOx) into less harmful substances (Correct answer)
- To cool exhaust gases before they exit the tailpipe
- To muffle exhaust noise
Correct answer: To convert harmful exhaust pollutants (HC, CO, NOx) into less harmful substances
The catalytic converter uses chemical reactions over precious metal catalysts to convert harmful hydrocarbons, carbon monoxide, and nitrogen oxides into water vapor, carbon dioxide, and nitrogen.
Question 2: A vehicle's power steering system is making a whining noise when turning. What is the most likely cause?
- Worn tie rod ends
- Low power steering fluid level (Correct answer)
- A loose serpentine belt
- Worn brake pads
Correct answer: Low power steering fluid level
Low power steering fluid causes the power steering pump to work harder and cavitate, producing a characteristic whining or groaning noise especially during turning.
Question 3: What is the main purpose of an engine's timing belt or timing chain?
- To drive the alternator and power steering pump
- To synchronize the crankshaft and camshaft rotation so valves open at the correct time (Correct answer)
- To connect the transmission to the driveshaft
- To drive the engine oil pump
Correct answer: To synchronize the crankshaft and camshaft rotation so valves open at the correct time
The timing belt/chain synchronizes the crankshaft and camshaft(s) to ensure intake and exhaust valves open and close at precisely the correct point in each piston's stroke.
Question 4: In automotive electrical systems, what does the term 'ground' refer to?
- The positive terminal of the battery
- The return path for electrical current, typically the vehicle's metal chassis (Correct answer)
- The fuse box location under the dashboard
- The voltage regulator output
Correct answer: The return path for electrical current, typically the vehicle's metal chassis
In automotive systems, the ground is the common return path for electrical current, using the vehicle's metal body and chassis to complete circuits back to the battery's negative terminal.
Question 5: What condition is indicated when white smoke pours from a vehicle's exhaust?
- Rich fuel mixture burning excess gasoline
- Coolant (antifreeze) is entering the combustion chamber and being burned (Correct answer)
- Normal operation on a cold day
- The catalytic converter is overheating
Correct answer: Coolant (antifreeze) is entering the combustion chamber and being burned
Persistent white smoke from the exhaust typically indicates coolant is leaking into the combustion chamber, often due to a blown head gasket or cracked cylinder head.
Question 6: What does the 'compression ratio' of an engine describe?
- The ratio of horsepower to engine displacement
- The ratio of cylinder volume at BDC to volume at TDC (Correct answer)
- The ratio of air to fuel in the mixture
- The ratio of intake pressure to exhaust pressure
Correct answer: The ratio of cylinder volume at BDC to volume at TDC
Compression ratio is the ratio of the total cylinder volume when the piston is at bottom dead center (BDC) to the volume when the piston is at top dead center (TDC).
Question 7: What is the purpose of 'tire rotation' as part of regular vehicle maintenance?
- To align the wheels to the manufacturer's specification
- To equalize tire wear by moving tires to different positions on the vehicle (Correct answer)
- To balance the tires by adding weights
- To check tire pressure and inflate to proper levels
Correct answer: To equalize tire wear by moving tires to different positions on the vehicle
Tire rotation moves tires between different axle positions to equalize uneven wear patterns caused by differences in load, steering forces, and drive forces at each position.
ASVAB Automotive Information 5
What is the purpose of a vehicle's catalytic converter?