Deck 5: Factors Affecting Engine Performance

Question 1

A leaking exhaust valve can affect the air/fuel mixture in a cylinder.

Answer 1

True

Question 2

During a running compression test, the pressures at a steady 2,500 rpm will be lower than the readings of a cranking compression test.

Answer 2

True

Question 3

A cylinder that has a dramatic increase during a wet compression test most likely has problems with piston rings.

Answer 3

True

Question 4

Compression testing is being discussed. Technician A says that the ignition should be disabled. Technician B says that the fuel system should be disabled. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 5

All of the following would most likely cause black smoke to emit from the exhaust pipe EXCEPT a ____.

A) shorted IAT sensor
B) faulty temperature sensor
C) defective fuel pressure regulator
D) defective MAP sensor

Question 6

Technician A says that a blown head gasket can cause coolant to mix with the engine oil to create a coffee-colored milkshake-like substance. Technician B says that white smoke from the exhaust pipe can be the result of a blown head gasket. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 7

Power balance testing is being discussed. Technician A says that during testing, a large drop in rpm indicates a cylinder that is not producing necessary power. Technician B says that on some vehicles, this test can be performed with a scan tool because of factory programing. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 8

Technician A says that the wrong spark plugs can cause preignition. Technician B says that preignition can possibly lead to engine damage. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 9

Head gaskets can leak combustion into the cooling system when they fail.

Question 10

A compression gauge is designed to tell the technician what the compression ratio of an engine is.

Question 11

The following compression results were taken from a 4-cylinder engine that started running poorly with no warning. What is the most likely cause?

A) blown head gasket
B) worn rings
C) worn cam lobes
D) broken rocker arms

Question 12

OEM parts are made by aftermarket manufacturers to exceed factory original specifications.

Question 13

Improper fuel can cause the valves in an engine to knock or rattle.

Question 14

Spark plugs can help identify problems with fuel, ignition, or mechanical issues.

Question 15

All of the following leaks could affect combustion in a cylinder EXCEPT ____.

A) head gasket
B) piston rings
C) valve seat
D) valve guide seal

Question 16

Compression test results are being discussed. Technician A says that if one cylinder is found to be low, a wet test should be performed to help narrow down the diagnoses. Technician B says that a difference of 10% between cylinders would be acceptable.

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 17

95 psi would be a typical cranking compression for a gasoline engine.

Question 18

Technician A says leaking valves could cause noticeable popping noises from the engine. Technician B says worn piston rings could cause a lack of power. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 19

Black smoke from the exhaust pipe is usually caused by coolant mixing in the combustion chamber.

Question 20

A car has come into a shop with an engine misfire. A power balance test has been performed with the following results.
Technician A says that cylinder 1 may have low compression. Technician B says that cylinders 2-3-4 are not working properly. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 21

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

Question 22

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

Question 23

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

Question 24

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

Question 25

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

Question 26

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

Question 27

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

Question 28

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

Question 29

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

Question 30

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

Question 31

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

Question 32

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

Question 33

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

Question 34

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

Question 35

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

Question 36

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

Question 37

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

Question 38

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

Question 39

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

Question 40

Which engine component is responsible for limiting crankshaft end play?

A) Rod bearings
B) Main bearings
C) Thrust bearing
D) None of the above

Question 41

Explain the procedure for using a chemical block tester to find combustion leaks in the cooling system.

Question 42

Improper spark plugs could cause preignition in the combustion chamber.

Question 43

When does detonation occur and what can it cause?

Question 44

Name the three types of abnormal combustion.

Question 45

Explain the function of a knock sensor.

Question 46

What does TSB stand for, and what is it?

Question 47

Describe briefly the basic steps in performing a cylinder leakage test on one cylinder.

Question 48

Preignition is more likely to cause engine damage than detonation.

Question 49

What sensor can cause the ignition timing to retard due to loose parts that rattle and make noise?

Question 50

What tool is best suited for finding rattles and noises?