ASE A1 (Engine Repair) 180 Q&A Test answers fully
explained for ideal study.
an engine miss is being diagnosed using a cylinder leakage test.
Technician A says that any cylinder with over 20% leakage has excessive leakage. Tech B says
that air leaking from the tailpipe indicates a cracked cylinder.
A only,
B only,
A & B,
Neither . - *correct Answer*A only:
If cylinder leakage exceeds 20%, check for air escaping the tailpipe, the PCV valve opening in
the rocker arm cover, and the top of the throttle body or carburetor.
Air leaking from the tailpipe usually indicates an exhaust valve leak
during a compression test, a cylinder has 40% of the specified compression reading. When the
tech performs a wet test, the compression reading on this cylinder has 75% of the specified
reading. The cause of the low compression reading could be
worn piston rings,
a burned exhaust valve,
a bent intake valve,
a worn camshaft lobe, - *correct Answer*worn piston rings
if compression increases during a wet test, this indicates worn piston rings. Compression would
not increase if an exhaust valve is burned, intake valve is bent, or camshaft lobe is worn.
the customer complains that the engine cranks but does not start; the first thing to check
should be
valve train operation,
battery voltage,
compression,
engine vacuum, - *correct Answer*valve train operation:
,if the engine cranks properly, the battery is not the problem. Compression would not be the
FIRST test, and because engine vacuum is low during a crank, a vacuum test would not be
conclusive.
during a cylinder balance test on an engine with fuel injection, one cylinder provides very little
rpm drop.
Tech A says the ignition system may be misfiring on that cylinder.
Tech B says the engine may have an intake manifold vacuum leak.
A only,
B only,
A & B,
Neither , - *correct Answer*Both A&B
Both a misfiring ignition system and an intake manifold leak could cause a cylinder to contribute
too little power
while discussing basic diagnostic procedures,
Tech A says the most complicated diagnostic tests should be performed first. Tech B says that
you should first question the customer to obtain as much info as possible about the problem
A,
B,
A & B,
Neither, - *correct Answer*B
Always attempt the more simple diagnosis first
with the engine idling, a vacuum gauge connected to the intake manifold fluctuates (from 15 to
20). These fluctuations may be caused by
late ignition timing,
intake manifold vacuum leaks,
a restricted exhaust system,
sticky valve stems and guides, - *correct Answer*sticky valve stems and guides
-late ignition timing would result in a low, steady reading
-intake manifold leaks would cause a very low, steady reading
-a restricted exhaust system would cause vacuum to slowly decrease after the engine was
accelerated and held steady
,oil is leaking from the crankshaft rear main bearing seal on an engine. Tech A says the oil seal
could be faulty. Tech B says the PCV system may not be functioning.
A,
B,
A & B,
Neither, - *correct Answer*A&B
A high-pitched squealing noise is heard during hard acceleration. This may be the cause of:
intake manifold leak,
the choke stuck closed
fuel system leak
small leak in exhaust manifold - *correct Answer*small leak in exhaust manifold
-intake manifold leak causes a high-pitched whistle at idle and low speeds
-carb choke stuck closed will not cause a high-pitched whistle
-fuel system leak normally would not cause a noise
a heavy thumping noise occurs with the engine idling, but the oil pressure is normal. this may
be caused by:
worn pistons and cylinders,
loose flywheel bolts,
worm main bearings,
loose camshaft bearings, - *correct Answer*loose flywheel bolts
-worn pistons and cylinders would cause a thumping noise during acceleration
-worn main bearings cause a thump when the engine is started
-loose camshaft bearings would cause a growling noise at all times
after a vehicle is parked overnight and then started in the morning, the engine has a lifter noise
that disappears after running for a short time. this may be caused by:
low oil pressure,
low oil level,
worn lifter bottom,
excessive lifter leak-down, - *correct Answer*excessive lifter leak-down
low oil pressure would result in a continuous noise
, low oil level would result in a continuous noise
worn lifter bottom would result in a continuous noise
when using a compression tester, the readings on the cylinders are all even, but lower than
spec. this could indicate:
blown head gasket,
carbon buildup,
cracked head,
worn rings and cylinders, - *correct Answer*worn rings and cylinders
-a low reading on two adjacent cylinders may indicate a blown head gasket
-carbon buildup would cause a high reading
-a low reading on two adjacent cylinders may indicate a cracked head
a cylinder balance test is being performed on an engine to determine which cylinder is causing
a miss.
Tech A says that when the faulty cylinder is disabled, engine rpm will drop more than for the
other cylinders.
Tech B says disabling the faulty cylinder will cause the engine to stall
A,
B,
Both,
Neither, - *correct Answer*Neither
the faulty cylinder will not cause the engine to stall, neither will it cause the engine to drop in
RPM since it is faulty.
an engine is idling at 750 rpm. the pointer on the vacuum gauge is floating between 11 and 16
in Hg. The most likely cause is
retarded timing,
advanced timing,
stuch EGR valve,
too lean idle mixture, - *correct Answer*too lean idle mixture
all others would not result in gauge fluctuation
the first step a Tech should take for diagnosis is:
explained for ideal study.
an engine miss is being diagnosed using a cylinder leakage test.
Technician A says that any cylinder with over 20% leakage has excessive leakage. Tech B says
that air leaking from the tailpipe indicates a cracked cylinder.
A only,
B only,
A & B,
Neither . - *correct Answer*A only:
If cylinder leakage exceeds 20%, check for air escaping the tailpipe, the PCV valve opening in
the rocker arm cover, and the top of the throttle body or carburetor.
Air leaking from the tailpipe usually indicates an exhaust valve leak
during a compression test, a cylinder has 40% of the specified compression reading. When the
tech performs a wet test, the compression reading on this cylinder has 75% of the specified
reading. The cause of the low compression reading could be
worn piston rings,
a burned exhaust valve,
a bent intake valve,
a worn camshaft lobe, - *correct Answer*worn piston rings
if compression increases during a wet test, this indicates worn piston rings. Compression would
not increase if an exhaust valve is burned, intake valve is bent, or camshaft lobe is worn.
the customer complains that the engine cranks but does not start; the first thing to check
should be
valve train operation,
battery voltage,
compression,
engine vacuum, - *correct Answer*valve train operation:
,if the engine cranks properly, the battery is not the problem. Compression would not be the
FIRST test, and because engine vacuum is low during a crank, a vacuum test would not be
conclusive.
during a cylinder balance test on an engine with fuel injection, one cylinder provides very little
rpm drop.
Tech A says the ignition system may be misfiring on that cylinder.
Tech B says the engine may have an intake manifold vacuum leak.
A only,
B only,
A & B,
Neither , - *correct Answer*Both A&B
Both a misfiring ignition system and an intake manifold leak could cause a cylinder to contribute
too little power
while discussing basic diagnostic procedures,
Tech A says the most complicated diagnostic tests should be performed first. Tech B says that
you should first question the customer to obtain as much info as possible about the problem
A,
B,
A & B,
Neither, - *correct Answer*B
Always attempt the more simple diagnosis first
with the engine idling, a vacuum gauge connected to the intake manifold fluctuates (from 15 to
20). These fluctuations may be caused by
late ignition timing,
intake manifold vacuum leaks,
a restricted exhaust system,
sticky valve stems and guides, - *correct Answer*sticky valve stems and guides
-late ignition timing would result in a low, steady reading
-intake manifold leaks would cause a very low, steady reading
-a restricted exhaust system would cause vacuum to slowly decrease after the engine was
accelerated and held steady
,oil is leaking from the crankshaft rear main bearing seal on an engine. Tech A says the oil seal
could be faulty. Tech B says the PCV system may not be functioning.
A,
B,
A & B,
Neither, - *correct Answer*A&B
A high-pitched squealing noise is heard during hard acceleration. This may be the cause of:
intake manifold leak,
the choke stuck closed
fuel system leak
small leak in exhaust manifold - *correct Answer*small leak in exhaust manifold
-intake manifold leak causes a high-pitched whistle at idle and low speeds
-carb choke stuck closed will not cause a high-pitched whistle
-fuel system leak normally would not cause a noise
a heavy thumping noise occurs with the engine idling, but the oil pressure is normal. this may
be caused by:
worn pistons and cylinders,
loose flywheel bolts,
worm main bearings,
loose camshaft bearings, - *correct Answer*loose flywheel bolts
-worn pistons and cylinders would cause a thumping noise during acceleration
-worn main bearings cause a thump when the engine is started
-loose camshaft bearings would cause a growling noise at all times
after a vehicle is parked overnight and then started in the morning, the engine has a lifter noise
that disappears after running for a short time. this may be caused by:
low oil pressure,
low oil level,
worn lifter bottom,
excessive lifter leak-down, - *correct Answer*excessive lifter leak-down
low oil pressure would result in a continuous noise
, low oil level would result in a continuous noise
worn lifter bottom would result in a continuous noise
when using a compression tester, the readings on the cylinders are all even, but lower than
spec. this could indicate:
blown head gasket,
carbon buildup,
cracked head,
worn rings and cylinders, - *correct Answer*worn rings and cylinders
-a low reading on two adjacent cylinders may indicate a blown head gasket
-carbon buildup would cause a high reading
-a low reading on two adjacent cylinders may indicate a cracked head
a cylinder balance test is being performed on an engine to determine which cylinder is causing
a miss.
Tech A says that when the faulty cylinder is disabled, engine rpm will drop more than for the
other cylinders.
Tech B says disabling the faulty cylinder will cause the engine to stall
A,
B,
Both,
Neither, - *correct Answer*Neither
the faulty cylinder will not cause the engine to stall, neither will it cause the engine to drop in
RPM since it is faulty.
an engine is idling at 750 rpm. the pointer on the vacuum gauge is floating between 11 and 16
in Hg. The most likely cause is
retarded timing,
advanced timing,
stuch EGR valve,
too lean idle mixture, - *correct Answer*too lean idle mixture
all others would not result in gauge fluctuation
the first step a Tech should take for diagnosis is:
