Deck 8: Engine and Misfire Diagnosis

Question 1

Which of the following is NOT likely to be an engine mechanical fault?

A) Poor fuel economy
B) Excessive oil consumption
C) Exhaust smoke
D) Engine noise

Answer 1

A

Question 2

A misfire is detected by what sensor(s)?

A) Knock sensor (KS)
B) Crankshaft position sensor (CKP)
C) Camshaft position sensor (CMP)
D) MAF and/or MAP

Answer 2

B

Question 3

How could a technician pinpoint a noise made by a defective rod bearing?

A) By disabling cylinders
B) By looking at spark plug gaps
C) By coasting in neutral
D) By removing the valve cover and listening while the engine is running

Answer 3

A

Question 4

Engine oil pressure is being measured. A good engine should be able to produce how much oil pressure?

A) More than 100 PSI
B) 10 PSI of more per 1,000 RPM
C) 20 PSI or less
D) 3-7 PSI at 2,500 RPM

Question 5

A good reading for a cylinder leakage test would be ________.

A) within 20% between cylinders
B) all cylinders above 20% leakage
C) all cylinders above 70% leakage and within 7% of each other
D) all cylinders below 20% leakage

Question 6

An engine in good condition should have about ________ in. Hg. vacuum at idle.

A) 17 to 21
B) no more than 15
C) 10 to 12
D) at least 29

Question 7

A cylinder contribution test is performed using a ________.

A) cylinder leakage tester
B) scan tool
C) digital storage oscilloscope (DSO)
D) compression gauge

Question 8

A relative compression test uses a DSO to monitor ________ to determine the relative compression of each cylinder in the engine while it is being cranked.

A) secondary ignition voltage
B) fuel pressure drop
C) battery draw by the starter motor
D) injector pulse-width

Question 9

When should a wet compression test be performed?

A) When a defective head gasket is suspected
B) Before a dry compression test
C) After a cylinder fails a dry compression test
D) When the engine is cold

Question 10

A running compression test is used to locate what type of engine problems?

A) Excessive exhaust system back pressure
B) Valve train-related faults
C) Piston or connecting rod faults
D) Leaking intake manifold gasket faults

Question 11

A P0300 DTC means ________.

A) that one cylinder has low compression
B) a fault with a fuel injector has been detected
C) a random misfire has been detected
D) a fault with the ignition system has been detected

Question 12

What test equipment is needed to view the pressure waveform inside the cylinder?

A) DSO and a pressure transducer
B) Compression tester and a DSO
C) Scan tool and compression gauge
D) Cylinder leakage tester and a scope

Question 13

A smoothly operating engine depends on ________.

A) Equal compression among cylinders
B) Cylinder compression levels above 100 psi (700 kPa) and within 70 psi (500 kPa) of each other
C) Compression levels below 100 psi (700 kPa) on most cylinders
D) High compression on most cylinders

Question 14

Technician A says that during a power balance test, the cylinder that causes the biggest RPM drop is the weak cylinder. Technician B says that if one spark plug wire is grounded out and the engine speed does not drop, a weak or dead cylinder is indicated. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 15

Which of the following is the least likely to cause an engine noise?

A) Carbon on the pistons
B) Cracked exhaust manifold
C) Vacuum leak
D) Loose accessory drive belt

Question 16

A good engine should produce how much compression during a running (dynamic) compression test?

A) 60-90 PSI
B) 30-60 PSI
C) 100-150 PSI
D) 150-200 PSI

Question 17

Technician A says that a leaking head gasket can be checked using a chemical tester. Technician B says that a leaking head gasket can be found using an exhaust gas analyzer. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 18

The low oil pressure warning light usually comes on ________.

A) whenever the oil filter bypass valve opens
B) whenever the oil filter antidrainback valve opens
C) whenever an oil change is required
D) whenever oil pressure drops dangerously low (4 to 7 psi)

Question 19

What does black exhaust smoke indicate?

A) Excessive fuel
B) Burning oil
C) Coolant in combustion chamber
D) Insufficient fuel

Question 20

What does blue exhaust smoke indicate?

A) Coolant in combustion chamber
B) Excessive fuel
C) Insufficient oil
D) Burning oil

Question 21

What does white smoke exhaust smoke indicate?

A) Excessive fuel
B) Insufficient fuel
C) Burning oil
D) Coolant in combustion chamber

Question 22

Technician A says to always wait five minutes before removing the radiator cap from a hot engine.
Technician B says that leaking coolant may cause a rust-colored stain. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 23

Which noise is most noticeable at idle?

A) Main-bearing knock
B) Piston slap
C) Worn thrust bearings
D) Valve lifters

Question 24

Which of the following is LEAST likely to create a rattle sound?

A) Loose accessory mounts
B) Broken harmonic balancer
C) Loose belt tensioner
D) Cracked flex plate

Question 25

Technician A says low oil pressure causes engine wear. Technician B says engine wear can cause low oil pressure. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 26

The following statements are all correct EXCEPT ________.

A) recommended oil pressure is 1 PSI for every 1000 RPM
B) oil pressure readings should be made at idle and 2500 RPM
C) oil pressure testing should be done at normal operating temperature
D) oil pressure may be tested by removing the oil pressure sending unit and installing a pressure gauge

Question 27

Technician A says that if the oil pressure warning light is on, the oil pressure should be checked with a manual gauge. Technician B says that a faulty electrical circuit could cause the oil pressure warning light to come on even when the oil pressure is good. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 28

Which of the following could result in low engine compression?

A) Damaged piston or piston ring
B) Cylinder head gasket
C) Damaged valve
D) All of these are correct.

Question 29

When preparing for a compression test, technician A disables the ignition system. Technician B only removes the spark plug for the cylinder he is testing. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 30

How many compression strokes should be used during a compression test?

A) One
B) Two
C) Four
D) Three

Question 31

When performing a cylinder leakage test, the following statements are all correct EXCEPT ________.

A) shop air should be applied to the dipstick tube
B) air heard escaping through the tailpipe may indicate a defective exhaust valve
C) shop air should be applied through the spark plug hole
D) bubbles in the coolant may indicate a defective head gasket

Question 32

While performing a cylinder leakage test, technician A says that 20% leakage is acceptable. Technician B says that a cylinder will show too much leakage if the piston is not at TDC on its compression stroke. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 33

A cylinder power balance test is performed. Cylinders 1, 2, and 3, all drop 175 RPM when disabled with a scan tool. Cylinder 4 drops 50 RPM when disabled. The following statements are all correct EXCEPT ________.

A) there may be a mechanical problem with cylinder 4
B) cylinder 4 is much stronger than 1, 2, and 3
C) this test could also be conducted by grounding the plug wire for each cylinder
D) cylinder 4 is much weaker than 1, 2, and 3

Question 34

Normal engine vacuum at idle is ________.

A) 17-21 in Hg
B) 3-6 in Hg
C) 3 PSI
D) 120 in Hg

Question 35

Technician A says a low but steady idle vacuum reading indicates a sticking valve. Technician B says a fluctuating vacuum gauge reading indicates incorrect ignition timing. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both technicians A and B
D) Neither technician A nor B

Question 36

Which of the following is NOT a cause of high exhaust back pressure?

A) Restricted muffler
B) Restricted catalytic converter
C) Vacuum leak
D) Restricted exhaust pipe

Question 37

Exhaust back pressure of an engine running at idle should be ________.

A) 2.5 PSI
B) 1.5 in. Hg
C) less than 1.5 PSI
D) 2.5 in. Hg