Question 1

Which of the following may contribute to detonation?

Accepted Answer

Detonation can be caused by a lean air/fuel mixture, which increases combustion temperatures, or by a malfunctioning EGR system, which fails to recirculate a portion of an engine's exhaust gas back to the engine cylinders, thereby not diluting the oxygen and not absorbing heat. Both conditions can lead to the abnormal combustion known as detonation.

Question 2

A scan tool is usually required to perform a compression test on a hybrid vehicle.

Accepted Answer

A scan tool is required to perform a compression test on a hybrid vehicle because the engine is not always running, and the scan tool can be used to force the engine to run in order to perform the test.

Question 3

If a low-compression cylinder is identified, a ___________ ___________ test can help determine where the pressure is going.

Accepted Answer

cylinder leakage

Question 4

Technician A says automatic transmission fluid is red and easily identified as a leak.Technician B says very old fluid may not appear red and may look like engine oil or power steering fluid.Who is correct?

Accepted Answer

Automatic transmission fluid is typically red, making it easier to identify as a leak, which is what Technician A says. Technician B is also correct because as the fluid ages, it can darken and may resemble engine oil or power steering fluid, making it harder to identify by color alone.

Question 5

A ___________ tester is used to diagnose a restricted exhaust system.

Accepted Answer

The answer of A ___________ tester is used to diagnose...

Question 6

A running compression test is done to check the breathing ability of the engine.

Accepted Answer

A running compression test, unlike a static compression test, is performed with the engine running and helps assess the engine's ability to draw in air, mix it with fuel, compress it, and then release exhaust gases, effectively evaluating its "breathing" capability.

Question 7

What type of noise will be caused by a piston slap?

Accepted Answer

Piston slap is a condition where there is excessive clearance between the piston and the cylinder wall, causing the piston to "slap" against the wall during operation. This typically produces a hollow, bell-like noise, most often occurring during cold engine warmup when the components have not yet expanded to their operating clearances.

Question 8

An engine with a blown head gasket will usually emit black smoke.

Accepted Answer

A blown head gasket typically results in white or gray smoke due to coolant burning in the combustion chamber, not black smoke, which is usually a sign of rich fuel mixture or incomplete combustion.

Question 9

White exhaust smoke indicates excessive fuel being burned.

Accepted Answer

White exhaust smoke typically indicates that coolant is being burned in the combustion chamber, not excessive fuel.

Question 10

If an engine is experiencing detonation, there may be a fault in the ___________ ________ circuit.

Accepted Answer

The answer of If an engine is experiencing detonation, there...

Question 11

If the timing belt breaks on a (an) ______________ engine, the valves can contact the pistons.

Accepted Answer

The answer of If the timing belt breaks on a...

Question 12

Which of these tools is used to perform a relative compression test?

Accepted Answer

An inductive ammeter is used to perform a relative compression test by measuring the current draw of the starter motor, which correlates with the compression in each cylinder.

Question 13

Black smoke emitted from a diesel engine indicates:

Accepted Answer

Black smoke from a diesel engine is typically a sign of a rich fuel mixture, meaning there is too much fuel and not enough air for complete combustion.

Question 14

Engine oil pressure testing is being discussed.Technician A says that oil pressure should be tested with the engine cold.Technician B says low oil pressure can mean that major engine repairs are needed.Who is correct?

Accepted Answer

Oil pressure should be tested with the engine at operating temperature, not cold. Low oil pressure can indicate serious engine issues that may require major repairs.

Question 15

Where should the piston be during a valve lash adjustment?

Accepted Answer

The piston should be at Top Dead Center (TDC) on the compression stroke during a valve lash adjustment to ensure the valves being adjusted are fully closed, allowing for accurate measurement and adjustment.

Question 16

Blue exhaust smoke means that engine oil is being burned in the combustion chamber.

Accepted Answer

Blue exhaust smoke is a clear indicator that engine oil is being burned within the combustion chamber, which can be due to various issues such as worn valve seals, damaged piston rings, or other internal engine problems.

Question 17

__________ __________ can display voltage and amperage over time, making them very useful for testing sensors and other components.

Accepted Answer

The answer of __________ __________ can display voltage and amperage...

Question 18

During a cylinder leakage test, air is heard coming from the throttle body.Which of these is the most likely cause?

Accepted Answer

A burned intake valve is the most likely cause of air being heard from the throttle body during a cylinder leakage test. This is because the intake valve's function is to let air into the cylinder, and if it's burned or damaged, air can leak back through the intake system, making a noise at the throttle body.

Question 19

The ________ is used to determine if each cylinder is contributing power to the overall engine output.

Accepted Answer

The power balance test is specifically designed to assess whether each cylinder in an engine is contributing equally to the engine's overall power output. By comparing the power output of each cylinder, mechanics can identify any cylinders that are underperforming.

Question 20

During a compression test, the pressure should not vary more than _________ percent between cylinders.

Accepted Answer

During a compression test, the pressure should not vary more than 10 percent between cylinders to ensure engine health and performance.

Quiz 23: Engine Mechanical Testing and Service