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ENGINE PERFORMANCE/QUESTIONS AND ANSWERS. STUDT GUIDE FOR EXAM PREP 2024 ACADEMIC YEAR
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ENGINE PERFORMANCE/QUESTIONS AND ANSWERS. STUDT GUIDE FOR EXAM PREP 2024 ACADEMIC YEAR
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ENGINE PERFORMANCE/QUESTIONS ANDANSWERS. STUDT GUIDE FOR EXAM PREP 2024
ACADEMIC YEAR
1. Blue smoke is coming from the exhaust pipe of a vehicle.
Tech A says that worn piston rings could be the cause. Tech B
says that a bad head gasket could be the cause. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither: A. Blue smoke means the engine is burning oil, which
could be caused by worn piston rings. Technician B is wrong because
a bad head gasket would cause coolant to leak into one or more
cylinders, resulting in white exhaust smoke.
2. A vacuum gauge is connected to the intake manifold engine
and the engine is run at 2,000 rpm. During the test, the pointer
on the gauge fluctuates rapidly between readings of 10 and 22
inches of vacuum. These test results point to:
A. a leaking intake manifold gasket
B. worn piston rings C. worn valve guides
D. a weak or broken valve spring: D. A leaking intake manifold gasket
or worn piston rings would not cause a vacuum gauge needle to
fluctuate. Worn valve guides would make the needle fluctuate at idle
but the needle would steady when engine speed is increased. A
weak or broken valve spring will cause a vacuum gauge to fluctuate
or jump from low to high readings.
3. Engine detonation (knock) could be caused by any of the
following EXCEPT:
A. a lean air/fuel mixture
B. retarded ignition timing
,C. excess carbon in the combustion chambers
D. a stuck-closed EGR valve: B. Advanced ignition timing will cause
knock, but retarded timing will not.
4. Tech A says that spark advance on an engine can be tested by
listening to the way the engine sounds at higher rpm. Tech B says
that spark advance on an engine can be tested with a timing light
that incorporates an ignition advance meter. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither: B. To accurately measure spark advance, use a timing
light that incorporates an ignition advance meter. The spark advance
cannot be determined by listening to the way the engine sounds.
5. A regular customer presents his vehicle for service. He
describes symptoms of poor drivability and says that the vehicle
has been repaired for the same problem in the past. Which, of
the following, should you do first?
A. connect the vehicle to an engine analyzer
B. check for diagnostic trouble codes C. check the vehicle
service history and check forTSBs, service campaigns and
recalls
D. perform a cylinder balance test: C. Checking the vehicle service
history may get you pointed in the right direction before you even raise
the hood. What repairs have been performed and what parts were
installed? What fixed the car before? If it is a recurring problem, maybe a
different course of action is in order. If the vehicle really has failed in the
same way, checking TSBs may provide information on updated parts that
weren't available previously and may solve the problem now. When
, ENGINE PERFORMANCE/QUESTIONS AND
ANSWERS. STUDT GUIDE FOR EXAM PREP 2024
ACADEMIC YEAR
checking for service campaigns and recalls, you may find that the
problem is a defect that the manufacturer will repair.
6. Two techs are listening to a tapping noise coming from the
top end of a V8 engine. Tech A says the noise could be a valve
needing adjustment. Tech B says the noise could be an
exhaust leak. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither: C. A tapping noise that does not dissipate after the
engine warms up could be caused by worn valvetrain components or
excessive valvetrain clearance. A similar type noise can sometimes
be caused by an exhaust leak at the exhaust manifold/cylinder head
juncture.
7. Tech A says a high spike line on an oscilloscope indicates
disconnected or open plug wire. Tech B says a high spike line
indicates a closed gap on a spark plug. Who is right?
A. Tech A
B. Tech B
C. Both
D. Neither: A. A higher-by-comparison spike line on an oscilloscope
could indicate a disconnected or open spark plug wire. If a spark
plug gap were closed, the oscilloscope would indicate a very low
spike line.
8. A vehicle can be started with great difficulty, but lacks power,
and will not idle. Tech A says that there could be a hole or tear
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