Engine Performance Questions and
Answers with Complete Solutions
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.
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.
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.
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.
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 for TSBs, 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 checking for service campaigns and recalls, you may find that the
problem is a defect that the manufacturer will repair.
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?
Answers with Complete Solutions
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.
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.
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.
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.
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 for TSBs, 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 checking for service campaigns and recalls, you may find that the
problem is a defect that the manufacturer will repair.
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?
