ASE Medium-Heavy Truck T1 Gasoline
Engines Practice Exam QUESTION AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
INSTANT DOWNLOAD PDF
1. A gasoline engine in a medium-heavy truck has low compression on two
adjacent cylinders. What is the MOST likely cause?
A. Burned exhaust valves
B. Worn piston rings
C. Blown head gasket
D. Cracked piston
A blown head gasket commonly fails between adjacent cylinders, causing
low compression in both.
2. Excessive crankcase pressure in a gasoline truck engine is MOST often
caused by:
A. Restricted PCV valve
B. Faulty oil pump
C. Clogged oil filter
D. Worn piston rings
Worn rings allow combustion gases to leak into the crankcase, increasing
pressure.
3. A technician finds oil consumption with blue exhaust smoke during
acceleration. The MOST likely cause is:
A. Valve guide seals
B. Worn piston rings
C. PCV restriction
D. Turbocharger failure
, Blue smoke under acceleration indicates oil passing the rings into the
combustion chamber.
4. Which tool is BEST for checking cylinder leakage on a gasoline engine?
A. Vacuum gauge
B. Compression gauge
C. Cylinder leak-down tester
D. Timing light
A leak-down tester pinpoints where compression is escaping.
5. A gasoline engine misfires only at idle. Which condition is MOST likely?
A. Vacuum leak
B. Restricted exhaust
C. Incorrect cam timing
D. Low fuel pressure
Vacuum leaks affect idle quality more than higher engine speeds.
6. Detonation in a medium-heavy truck gasoline engine can be caused by:
A. Retarded ignition timing
B. Low-octane fuel
C. Rich air-fuel mixture
D. Cold intake air
Low-octane fuel ignites prematurely under load, causing detonation.
7. When checking engine oil pressure, the MOST accurate method is to use:
A. Scan tool data
B. Mechanical oil pressure gauge
C. Warning lamp
D. Dash gauge
A mechanical gauge provides direct, accurate oil pressure readings.
8. Low oil pressure at idle but normal at higher RPM indicates:
A. Worn oil pump gears
B. Excessive bearing clearance
C. Clogged pickup screen
D. Incorrect oil viscosity
Worn bearings allow oil to escape at low speeds, reducing pressure.
, 9. A gasoline engine backfires through the intake. The MOST likely cause is:
A. Lean mixture
B. Restricted exhaust
C. Incorrect ignition timing
D. Low compression
Intake backfire is commonly caused by timing that is too advanced or a
crossed ignition.
10.Which condition will cause a vacuum gauge reading to fluctuate rapidly?
A. Late valve timing
B. Burned valve
C. Restricted exhaust
D. Normal engine operation
A burned valve causes intermittent sealing, creating rapid needle
movement.
11.Excessive oil foaming is MOST often caused by:
A. Low oil level
B. Overfilled crankcase
C. Restricted PCV system
D. Incorrect oil filter
Too much oil allows the crankshaft to whip air into the oil.
12.A cracked exhaust manifold may cause:
A. Rich mixture
B. Oxygen sensor false readings
C. Increased oil pressure
D. Valve train noise only
Exhaust leaks allow outside air to affect O2 sensor readings.
13.Which test is BEST for verifying camshaft lobe wear?
A. Compression test
B. Vacuum test
C. Cam lift measurement
D. Leak-down test
Measuring lobe lift confirms camshaft wear.
Engines Practice Exam QUESTION AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A
INSTANT DOWNLOAD PDF
1. A gasoline engine in a medium-heavy truck has low compression on two
adjacent cylinders. What is the MOST likely cause?
A. Burned exhaust valves
B. Worn piston rings
C. Blown head gasket
D. Cracked piston
A blown head gasket commonly fails between adjacent cylinders, causing
low compression in both.
2. Excessive crankcase pressure in a gasoline truck engine is MOST often
caused by:
A. Restricted PCV valve
B. Faulty oil pump
C. Clogged oil filter
D. Worn piston rings
Worn rings allow combustion gases to leak into the crankcase, increasing
pressure.
3. A technician finds oil consumption with blue exhaust smoke during
acceleration. The MOST likely cause is:
A. Valve guide seals
B. Worn piston rings
C. PCV restriction
D. Turbocharger failure
, Blue smoke under acceleration indicates oil passing the rings into the
combustion chamber.
4. Which tool is BEST for checking cylinder leakage on a gasoline engine?
A. Vacuum gauge
B. Compression gauge
C. Cylinder leak-down tester
D. Timing light
A leak-down tester pinpoints where compression is escaping.
5. A gasoline engine misfires only at idle. Which condition is MOST likely?
A. Vacuum leak
B. Restricted exhaust
C. Incorrect cam timing
D. Low fuel pressure
Vacuum leaks affect idle quality more than higher engine speeds.
6. Detonation in a medium-heavy truck gasoline engine can be caused by:
A. Retarded ignition timing
B. Low-octane fuel
C. Rich air-fuel mixture
D. Cold intake air
Low-octane fuel ignites prematurely under load, causing detonation.
7. When checking engine oil pressure, the MOST accurate method is to use:
A. Scan tool data
B. Mechanical oil pressure gauge
C. Warning lamp
D. Dash gauge
A mechanical gauge provides direct, accurate oil pressure readings.
8. Low oil pressure at idle but normal at higher RPM indicates:
A. Worn oil pump gears
B. Excessive bearing clearance
C. Clogged pickup screen
D. Incorrect oil viscosity
Worn bearings allow oil to escape at low speeds, reducing pressure.
, 9. A gasoline engine backfires through the intake. The MOST likely cause is:
A. Lean mixture
B. Restricted exhaust
C. Incorrect ignition timing
D. Low compression
Intake backfire is commonly caused by timing that is too advanced or a
crossed ignition.
10.Which condition will cause a vacuum gauge reading to fluctuate rapidly?
A. Late valve timing
B. Burned valve
C. Restricted exhaust
D. Normal engine operation
A burned valve causes intermittent sealing, creating rapid needle
movement.
11.Excessive oil foaming is MOST often caused by:
A. Low oil level
B. Overfilled crankcase
C. Restricted PCV system
D. Incorrect oil filter
Too much oil allows the crankshaft to whip air into the oil.
12.A cracked exhaust manifold may cause:
A. Rich mixture
B. Oxygen sensor false readings
C. Increased oil pressure
D. Valve train noise only
Exhaust leaks allow outside air to affect O2 sensor readings.
13.Which test is BEST for verifying camshaft lobe wear?
A. Compression test
B. Vacuum test
C. Cam lift measurement
D. Leak-down test
Measuring lobe lift confirms camshaft wear.
