Deck 48: Diagnosing Engine Performance Problems

Question 1

A collapsed laminated (two-layer) exhaust pipe will often cause a stripe of discoloration on the outside of the pipe at the point of restriction.

Answer 1

True

Question 2

A(n) ____________________ is a popular machine used to locate vacuum, oil, cooling, and exhaust leaks.

Answer 2

smoke tester

Question 3

Which of the following is the LEAST-Likely cause of a compression leak?

A)Worn piston rings
B)A timed spark
C)Broken piston rings
D)Burned valves

Answer 3

B

Question 4

While having a discussion, Technician A says that a compression test will tell the condition of oil control rings and compression rings. Technician B says that the compression test will only tell the condition of compression rings. Who is correct?

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

Question 5

Running compression should MOST-Likely be about:

A)5% of cranking compression
B)50% of cranking compression
C)60% of cranking compression
D)80% of cranking compression

Question 6

A gummy deposit buildup behind the throttle plate can be caused by poor quality fuel, blowby, and exhaust gas recirculation (EGR) gases.

Question 7

The spark created by the ignition system must be delivered to the correct spark plug at a specified point after top dead center (TDC).

Question 8

All of the following statements are true EXCEPT:

A)catalytic converters can become plugged if they operate for a prolonged period when there is a misfire.
B)as a general rule, exhaust backpressure should not exceed 3.75 psi at wide-open throttle (WOT) under full load.
C)a rich air-fuel mixture can result in a plugged converter when it overheats and melts internally.
D)exhaust backpressure can be tested by removing the oxygen (O₂) sensor and connecting a pressure tester using a special fitting.

Question 9

Which of the following is LEAST-Likely an advantage of a leakage test over a compression test?

A)The leakage test can be performed on an engine that is removed from a vehicle.
B)A performance camshaft will not affect the results of the test.
C)The exact source of leakage can be pinpointed before engine disassembly.
D)Acceptable leakage on the tester's gauge is usually less than 20% to 25%.

Question 10

The item that can MOST-Likely cause an engine to have increased compression, which can cause fuel to detonate in the cylinder is:

A)water
B)zinc
C)carbon
D)oil

Question 11

Low compression can result from engine breathing problems and ____________________.

Question 12

Sometimes an engine starts and runs but one cylinder has a dead misfire.

Question 13

While having a discussion, Technician A says that dry black soot at the exhaust pipe indicates an overly rich air-fuel mixture. Technician B says that it indicates oil consumption. Who is correct?

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

Question 14

A fast way of locating a weak cylinder is with a cylinder power balance test. Then a ____________________ or leakage test can be performed to further pinpoint the cause of the problem.

Question 15

Above idle speed, symptoms of a leaking manifold diminish but still show up on the vacuum gauge.

Question 16

A(n) ____________________ is indicated when the needle drops at regular intervals.

Question 17

The ____ can pinpoint causes of combustion chamber leakage.

A)wet compression test
B)cranking compression test
C)cylinder leakage test
D)cranking vacuum test

Question 18

All of the following statements are true EXCEPT:

A)an exhaust system takes about 2 minutes to fill with smoke.
B)finding coolant leaks with smoke can be done with the cooling system drained.
C)vacuum leaks are located with the engine on and the throttle closed.
D)manifold leaks can be tested using smoke and a mirror and flashlight.

Question 19

A traditional ____________________ test measures how well a cylinder is sealed by the cylinder head gasket, piston rings, and valves.

Question 20

Dirty fuel injectors can cause driveability problems and ____ at full throttle.

A)detonation
B)cranking
C)engine knock
D)spark knock

Question 21

How would you perform a wet compression test?

Question 22

What three events should occur in order for an engine to start running properly?

Question 23

Sometimes, a V-type engine can have a vacuum leak between the underside of the intake manifold and the crankcase. Describe one way to test for this.

Question 24

How would you test for a restricted exhaust?

Question 25

How would you perform a cranking vacuum test?