ASVAB Auto and Shop: Engine Systems and Repair 5

Question 1

What is the purpose of the exhaust gas recirculation (EGR) system?

Accepted Answer

Reduce NOx emissions by recirculating a portion of exhaust gas into the intake

Answer

The EGR system recirculates a small amount of exhaust gas back into the intake to lower combustion temperature, reducing harmful nitrogen oxide (NOx) emissions.

Question 2

When replacing a timing chain, what additional component should typically be replaced at the same time?

Accepted Answer

Timing chain tensioner and guides

Answer

Tensioners and guides wear along with the timing chain, so replacing them together prevents premature chain failure after a fresh installation.

Question 3

What does a higher compression ratio in a gasoline engine generally indicate?

Accepted Answer

Higher potential power output but requiring higher-octane fuel

Answer

Higher compression ratios extract more energy from combustion, increasing power output, but require higher-octane fuel to prevent detonation.

Question 4

What type of valve train arrangement has the camshaft mounted directly in the cylinder head?

Accepted Answer

Overhead camshaft (OHC)

Answer

In an overhead camshaft (OHC) design, the camshaft sits in the cylinder head, operating valves directly or via short rocker arms for improved high-RPM performance.

Question 5

A car's engine oil appears milky or frothy on the dipstick. What does this indicate?

Accepted Answer

Coolant has mixed with the engine oil, likely due to a head gasket failure

Answer

Milky, frothy oil indicates that coolant has entered the oil system, which typically results from a blown head gasket or cracked engine block.

ASVAB - Armed Services Vocational Aptitude Battery Practice Test

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ASVAB Auto and Shop: Engine Systems and Repair 5