Question 1

What color smoke is caused by an engine that is burning oil in the combustion chamber?

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Question 2

Technician A says that noise from piston slap usually starts out by making noise when the engine is cold and goes away after it reaches operating temperature. Technician B says that replacing the oil pump will stop the noise created by piston slap. Who is correct?
A) A only
B) B only
C) Both A and B
D) Neither A nor B

Accepted Answer

Technician A is correct. Piston slap is usually heard when the engine is cold and goes away as it reaches operating temperature. Technician B is incorrect because replacing the oil pump will not stop the noise created by piston slap.

Question 3

What test would be performed to identify a cylinder that may not be running as efficiently as the others without removing the spark plugs?

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Question 4

Which test will most accurately pinpoint the finding of a failed intake valve?
A) cranking compression test
B) cylinder leakage test
C) vacuum test
D) running compression test

Accepted Answer

A cylinder leakage test can accurately pinpoint the finding of a failed intake valve by measuring the amount of pressure lost from the cylinder through the valve. This test involves applying air pressure to the cylinder and measuring the pressure lost through various openings, including the intake valve. The other tests may not provide as clear of an indication of a failed intake valve.

Question 5

What could cause a red or orange tint to be present on the electrodes?

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Question 6

What term describes the condition where a cylinder does not combust properly and produce power?

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Question 7

Which of the following would most likely cause a low running compression reading on one cylinder?
A) clogged air filter
B) worn cam lobe
C) cracked throttle plate
D) timing belt jumped time

Accepted Answer

A worn cam lobe would cause a low running compression reading on one cylinder by not allowing the valve to fully open and close, resulting in incomplete combustion and lower pressure in that cylinder. A clogged air filter, cracked throttle plate, and timing belt jumped time would not typically cause a low compression reading on just one cylinder.

Question 8

What term is used to describe the ability of the fuel to vaporize?

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Question 9

An engine is idling rough and has a lack of power. Which test should be performed first?
A) Cranking compression test
B) Running compression test
C) Cylinder leakage test
D) Cylinder power balance test

Accepted Answer

A cylinder power balance test is the best choice as it can help identify which cylinder(s) are not contributing to the engine's power and causing the rough idle. A cranking compression test, running compression test, and cylinder leakage test may also be necessary, but it is best to perform the power balance test first.

Question 10

Technician A says that excessive clearance on a rod bearing can cause a knocking sound from the engine bottom end. Technician B says that a cracked flexplate can cause a knocking sound from the engine bottom end. Who is correct?
A) A only
B) B only
C) Both A and B
D) Neither A nor B

Accepted Answer

Excessive clearance on a rod bearing can cause a knocking sound from the engine bottom end because it allows the connecting rod to move around excessively, leading to metal-to-metal contact with the rod journal on the crankshaft. Similarly, a cracked flexplate can also cause a knocking sound from the engine bottom end because it causes the torque converter to hit against the flexplate and create a knocking noise. Therefore, both Technician A and Technician B are correct.

Question 11

A running compression test is being performed. Technician A says a low reading could be caused by a worn camshaft lobe. Technician B says low reading could be caused by an excessively worn lifter. Who is correct?
A) Technician A
B) Technician B
C) Both A and B
D) Neither A nor B

Accepted Answer

Both Technician A and B are correct. A worn camshaft lobe can result in low compression in one or more cylinders. Similarly, an excessively worn lifter can also cause low compression in a cylinder.

Question 12

What component maintains the correct fuel pressure in the fuel rail?

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Question 13

Which of the following is most likely to cause a light tapping or ticking noise from the engine?
A) Worn rod bearings
B) Incorrect crankshaft end play
C) Incorrect valve adjustment
D) Worn timing chain

Accepted Answer

An incorrect valve adjustment can cause a light tapping or ticking noise from the engine as the valves may not be opening or closing properly. Worn rod bearings (A) typically produce a knocking noise, while incorrect crankshaft end play (B) and a worn timing chain (D) usually result in a rattling or clattering noise.

Question 14

What component is most likely to cause valvetrain clatter immediately following an oil change?

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Question 15

On what stroke and crankshaft position does the ignition system begin the spark process to ignite the air-fuel mixture?

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Question 16

A cylinder is reading a 100 percent leakage during a cylinder leakage test. Technician A says the exhaust valve could be open. Technician B says the exhaust valve could be bent. Who is correct?
A) Technician A
B) Technician B
C) Both A and B
D) Neither A nor B

Accepted Answer

Both Technician A and Technician B are correct. If the exhaust valve is open or bent, it will cause a 100 percent leakage during a cylinder leakage test.

Question 17

A cylinder leakage test is being performed. What is the most likely cause when air is blowing out through the radiator?
A) cracked intake manifold
B) crack at the bottom of a cylinder
C) bad water pump
D) blown head gasket

Accepted Answer

Air blowing out through the radiator indicates a blown head gasket, which allows compressed air from the cylinder to escape into the engine's cooling system and be forced out through the radiator. A cracked intake manifold or a bad water pump would not cause air to blow out through the radiator, and a crack at the bottom of a cylinder would not necessarily be related to the cooling system.

Question 18

What would you expect to see on the electrodes of a set of spark plugs removed from an engine that was running too rich?

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Question 19

During a cylinder leakage test, what is the most likely cause of air blowing out through the exhaust pipe?

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Question 20

Which engine component is responsible for limiting crankshaft end play?
A) Rod bearings
B) Main bearings
C) Thrust bearing
D) None of the above

Accepted Answer

The thrust bearing is specialized in controlling the axial movement (movement forward and backward) of the crankshaft, which helps limit crankshaft end play. Rod bearings and main bearings, on the other hand, are responsible for supporting the connecting rods and crankshaft journals respectively.

Quiz 5: Factors Affecting Engine Performance

What color smoke is caused by an engine that is burning oil in the combustion chamber?

Technician A says that noise from piston slap usually starts out by making noise when the engine is cold and goes away after it reaches operating temperature. Technician B says that replacing the oil pump will stop the noise created by piston slap. Who is correct?

What test would be performed to identify a cylinder that may not be running as efficiently as the others without removing the spark plugs?

Which test will most accurately pinpoint the finding of a failed intake valve?

What could cause a red or orange tint to be present on the electrodes?

What term describes the condition where a cylinder does not combust properly and produce power?

Which of the following would most likely cause a low running compression reading on one cylinder?

What term is used to describe the ability of the fuel to vaporize?

An engine is idling rough and has a lack of power. Which test should be performed first?

Technician A says that excessive clearance on a rod bearing can cause a knocking sound from the engine bottom end. Technician B says that a cracked flexplate can cause a knocking sound from the engine bottom end. Who is correct?

A running compression test is being performed. Technician A says a low reading could be caused by a worn camshaft lobe. Technician B says low reading could be caused by an excessively worn lifter. Who is correct?

What component maintains the correct fuel pressure in the fuel rail?

Which of the following is most likely to cause a light tapping or ticking noise from the engine?

What component is most likely to cause valvetrain clatter immediately following an oil change?

On what stroke and crankshaft position does the ignition system begin the spark process to ignite the air-fuel mixture?

A cylinder is reading a 100 percent leakage during a cylinder leakage test. Technician A says the exhaust valve could be open. Technician B says the exhaust valve could be bent. Who is correct?

A cylinder leakage test is being performed. What is the most likely cause when air is blowing out through the radiator?

What would you expect to see on the electrodes of a set of spark plugs removed from an engine that was running too rich?

During a cylinder leakage test, what is the most likely cause of air blowing out through the exhaust pipe?

Which engine component is responsible for limiting crankshaft end play?