ASE A1 (Engine Repair) Practice Test with
complete solutions 2024/2025
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 . - 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, - 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, - 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 , - 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, - 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, - 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, - 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 - 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, - 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, - 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, - 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, - 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.
