22 A1 — Engine Repair Practice Questions & Answers

1. 1. A cranking compression test is performed on a warm engine with all spark plugs removed, the throttle held wide open, and the fuel and ignition systems disabled. The readings are 152, 149, 155, and 118 psi. Which statement best describes how these results should be interpreted?

   • A.No conclusion is possible from a cranking test; only a running compression test can be interpreted.
   • B.All four readings are acceptable because each one is above 100 psi.
   • C.Only the average of the four readings matters, and that average is acceptable.
   • D.The cylinder reading 118 psi must be investigated, because it is more than about 10% below the highest cylinder.✓ Answer

   On a cranking compression test, consistency between cylinders carries more diagnostic weight than the absolute number, because absolute pressure varies with cranking speed, altitude, engine design, and gauge. Standard practice is that no cylinder should read more than roughly 10% below the highest cylinder; 118 psi is about 24% below 155 psi, so that cylinder must be followed up with a wet test or a cylinder leakage test.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — perform cranking compression test and determine needed action; industry ~10% cylinder-to-cylinder variation guidelineReport a problem with this question

2. 2. One cylinder reads low during a dry cranking compression test. A small amount of clean engine oil is squirted through the spark plug hole and the test is repeated; the reading rises substantially. What does this indicate?

   • A.Worn piston rings or a worn/scored cylinder wall✓ Answer
   • B.A head gasket leaking into the coolant jacket
   • C.A burnt or improperly seated valve
   • D.A camshaft lobe worn flat on that cylinder

   The oil temporarily seals the gap between the rings and the cylinder wall, so a large jump in pressure proves the leak path was past the rings. If the reading had stayed about the same, the leak would be past a valve or through the head gasket, because oil poured on top of the piston cannot seal those paths.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — perform cranking (dry and wet) compression test and interpret resultsReport a problem with this question

3. 3. An engine loses coolant with no visible external leak. Cranking compression on cylinders 1 through 4 reads 148, 74, 70, and 151 psi. Cylinders 2 and 3 are next to each other in the block. What is the MOST likely cause?

   • A.Worn piston rings in cylinders 2 and 3
   • B.A head gasket failure between cylinders 2 and 3✓ Answer
   • C.A restricted exhaust system
   • D.A broken camshaft drive belt or chain

   Two adjacent cylinders reading nearly the same low value is the classic signature of a head gasket that has failed across the narrow land between them, so each cylinder bleeds into the other during the compression stroke. Coolant disappearing with no external leak supports an internal gasket breach, while ring wear would not affect exactly two neighboring cylinders equally or explain the coolant loss.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — diagnose engine problems from compression test results; Area B (Cylinder Head and Valve Train) head gasket diagnosisReport a problem with this question

4. 4. An engine cranks quickly and smoothly but will not start. A compression test shows almost no compression in every cylinder. What should the technician suspect FIRST?

   • A.A restricted exhaust system
   • B.A broken or jumped camshaft drive belt or chain✓ Answer
   • C.A blown head gasket
   • D.Worn piston rings throughout the engine

   When every cylinder is equally near zero, the fault has to be something common to all of them — the valves are no longer opening and closing in time with the crankshaft, so no cylinder can seal and build pressure. Ring and gasket failures occur cylinder by cylinder, and the unusually fast, smooth cranking is itself a clue that the engine is building no compression at all.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — determine if a crank-no-start condition is engine-mechanical; Area B — inspect and verify valve timingReport a problem with this question

5. 5. During a cylinder leakage (leak-down) test, a cylinder is brought to top dead center on the compression stroke and pressurized with shop air. Air is heard escaping from the tailpipe. What does this indicate?

   • A.Worn piston rings or a damaged cylinder wall
   • B.A leaking (not seating) exhaust valve✓ Answer
   • C.A leaking head gasket
   • D.A leaking intake valve

   The only path from the combustion chamber to the tailpipe is through the exhaust port, so audible air there proves the exhaust valve is not sealing against its seat. The same test identifies other leak paths by where the air comes out: at the throttle body or intake it is the intake valve, at the oil fill or dipstick tube it is the rings or cylinder, and bubbles in the radiator mean a head gasket or a crack.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — perform cylinder leakage test and determine the source of the leakageReport a problem with this question

6. 6. Two technicians discuss cylinder leakage test results. Technician A says air heard escaping from the oil filler opening or dipstick tube points to worn rings, a worn cylinder wall, or a damaged piston. Technician B says bubbles rising in the radiator during the test point to a leaking head gasket or a crack in the head or block. Who is correct?

   • A.Technician B only
   • B.Neither Technician A nor Technician B
   • C.Technician A only
   • D.Both Technician A and Technician B✓ Answer

   Both statements follow the same principle: the escape point identifies the failed sealing surface. Pressurized air that reaches the crankcase had to pass the piston rings or a damaged cylinder wall, and air that reaches the coolant jacket had to cross a head gasket or a crack, which is why it surfaces as bubbles in the radiator.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — perform cylinder leakage test and determine the source of the leakageReport a problem with this question

7. 7. A knocking noise is heard only when the automatic transmission is placed in gear; it disappears in Park and Neutral at the same engine speed. Oil pressure is normal and the noise does not change with engine temperature. What is the MOST likely cause?

   • A.A worn connecting rod bearing
   • B.Excessive piston-to-cylinder-wall clearance
   • C.A collapsed hydraulic lifter
   • D.A cracked flexplate or a torque converter fault✓ Answer

   A crack in the flexplate or a converter defect is only loaded when the converter has to transmit torque, so selecting a gear makes the noise appear and Park or Neutral unloads it. Internal bearing and valve-train noises are produced by combustion and rotating loads that are present regardless of gear selection, so they do not vanish in Neutral.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — identify engine noises and determine needed action; Area C — inspect flywheel/flexplate and ring gearReport a problem with this question

8. 8. A hollow, muffled rapping noise is loudest at idle when the engine is first started cold and becomes much quieter as the engine reaches operating temperature. What is the MOST likely cause?

   • A.A worn connecting rod bearing
   • B.Excessive crankshaft end play
   • C.Excessive piston-to-cylinder-wall clearance (piston slap)✓ Answer
   • D.A worn main bearing

   An aluminum piston expands more than the surrounding bore as it heats, so an oversized clearance closes up and the piston stops rocking and slapping against the cylinder wall once the engine is warm. Bearing noises behave the opposite way: they persist or worsen when the engine is hot because the oil film thins as oil temperature rises.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — identify engine noises and determine needed action; Area C — identify piston and cylinder wear patternsReport a problem with this question

9. 9. A heavy, metallic knock is loudest above about 2,500 rpm under acceleration and is also heard when the throttle is closed quickly. The noise does not change between Park and Drive and does not fade as the engine warms up. What is the MOST likely cause?

   • A.Piston slap
   • B.A worn connecting rod bearing✓ Answer
   • C.A loose accessory drive belt
   • D.A sticking hydraulic lifter

   Excessive rod bearing clearance lets the rod hammer the journal each time the load direction reverses — combustion pushes the rod down under acceleration and inertia pulls it back when the throttle snaps closed — which is why the knock is heard both on power and on the overrun. Piston slap would fade with warm-up, lifter noise is a light tick at half crankshaft speed heard at the valve cover, and a loose belt makes a squeal or chirp rather than a load-sensitive knock.

   Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — identify engine noises and determine needed action; Area C — inspect connecting rods and bearingsReport a problem with this question

10. 10. This question contains the word EXCEPT. Read the question carefully and choose the answer that does NOT fit. Continuous blue-gray smoke from the tailpipe together with high oil consumption may be caused by any of the following EXCEPT:

    • A.A leaking valve cover gasket that drips oil onto the exhaust manifold✓ Answer
    • B.Excessive cylinder bore taper and out-of-round wear
    • C.Worn valve guides and deteriorated valve stem seals
    • D.Worn or broken piston rings

    Blue smoke at the tailpipe means oil is reaching the combustion chamber and being burned there, which happens past worn rings, a worn or out-of-round bore, or worn guides and stem seals. A leaking valve cover gasket loses oil outside the engine; the oil burns on the hot manifold and produces smoke and odor from the engine compartment, but it never enters the cylinder, so it cannot cause blue exhaust smoke.

    Source: ASE A1 Engine Repair task list, Area A (General Engine Diagnosis) — diagnose excessive oil consumption and abnormal exhaust color; Area B — inspect valve guides and replace valve stem sealsReport a problem with this question

11. 11. An engine overheats, the cooling system will not hold pressure during a pressure test although no external leak can be found, and there is persistent white smoke with a sweet odor from the tailpipe. What is the MOST likely cause?

    • A.A weak radiator pressure cap
    • B.A blown head gasket✓ Answer
    • C.A restricted heater core
    • D.A thermostat stuck open

    Losing pressure with no external leak means coolant is escaping into the engine, and white sweet-smelling exhaust is coolant being vaporized in the combustion chamber; combustion gases forced the other way into the coolant then cause the overheating. A weak cap would leak at the cap and cause boil-over while the rest of the system still held pressure, a stuck-open thermostat causes slow warm-up rather than overheating, and a restricted heater core causes no heat without affecting engine temperature.

    Source: ASE A1 Engine Repair task list, Area D (Lubrication and Cooling Systems) — perform cooling system pressure and leak tests; Area B — head gasket diagnosisReport a problem with this question

12. 12. An engine runs at normal temperature in stop-and-go traffic but overheats during sustained high-speed highway driving. The coolant level is correct, the system holds pressure, and the thermostat opens at the specified temperature. Which is the MOST likely cause?

    • A.A worn belt tensioner that lets the water pump belt slip under high load✓ Answer
    • B.A restricted heater core
    • C.A cooling fan or fan clutch that does not engage
    • D.A pressure cap with a rating slightly higher than specified

    At highway speed ram air through the radiator is at its maximum and the fan contributes almost nothing, so overheating that appears only at high rpm and load points to inadequate coolant circulation — a belt slipping because the tensioner is worn, an eroded pump impeller, or a restricted radiator core. A fan or fan-clutch fault produces the opposite pattern: overheating at idle and low speed that clears once the vehicle is moving.

    Source: ASE A1 Engine Repair task list, Area D (Lubrication and Cooling Systems) — inspect and test water pump, drive belts, pulleys and tensioners, and cooling fans/fan clutchReport a problem with this question

13. 13. An engine takes an unusually long time to warm up and the heater only blows cool air, but the engine never overheats. Technician A says a thermostat stuck closed is the cause. Technician B says a weak radiator pressure cap is the cause. Who is correct?

    • A.Technician B only
    • B.Technician A only
    • C.Neither Technician A nor Technician B✓ Answer
    • D.Both Technician A and Technician B

    Slow warm-up with no heat and no overheating is the signature of a thermostat stuck OPEN, which lets coolant circulate through the radiator continuously so the engine never reaches its controlled operating temperature. A thermostat stuck closed produces the opposite symptom — rapid overheating because flow to the radiator is blocked — and a weak pressure cap lowers the boiling point and causes coolant loss and boil-over, not slow warm-up.

    Source: ASE A1 Engine Repair task list, Area D (Lubrication and Cooling Systems) — inspect and test thermostat, bypass, and housing; inspect and test pressure cap and recovery systemReport a problem with this question

14. 14. The oil pressure warning lamp glows at hot idle and goes out as engine speed increases. There are no unusual engine noises, and the oil level and condition are correct. What should the technician do FIRST?

    • A.Refill the engine with a heavier viscosity oil to raise the pressure
    • B.Connect a mechanical (direct-reading) oil pressure gauge and compare actual pressure to specification at the specified rpm and temperature✓ Answer
    • C.Replace the oil pump
    • D.Replace the main and connecting rod bearings

    The lamp and its sending unit only report that pressure is below a switching threshold, and the lamp, sender, or wiring can themselves be at fault, so the reading must be confirmed before any engine part is condemned. A mechanical gauge shows the true pressure at the specified rpm and oil temperature; only if actual pressure is low do causes such as a worn pump, a stuck-open relief valve, a plugged pickup screen, or excessive bearing clearance come into play. Switching to a heavier oil masks the symptom instead of diagnosing it.

    Source: ASE A1 Engine Repair task list, Area D (Lubrication and Cooling Systems) — diagnose engine lubrication system problems and perform oil pressure testsReport a problem with this question

15. 15. An oil pump has been removed for inspection. Which tools and method are used to check rotor (or gear) end clearance and the flatness of the pump cover?

    • A.A telescoping gauge read with an outside micrometer
    • B.A precision straightedge laid across the pump with a feeler gauge inserted under it✓ Answer
    • C.A dial indicator mounted on a magnetic base
    • D.Plastigage laid across the rotor faces and crushed by the cover

    End clearance is the gap between the rotor or gear face and the flat cover, so it is measured by spanning the pump body with a known-flat reference and sliding feeler gauges into the gap; the same straightedge-and-feeler method reveals wear or warpage in the cover itself. Plastigage is intended for bearing oil clearance, and a telescoping gauge with a micrometer measures bore diameters, neither of which fits a flat side clearance. Excessive end clearance lets oil bleed internally past the rotors and lowers system pressure.

    Source: ASE A1 Engine Repair task list, Area D (Lubrication and Cooling Systems) — inspect oil pump gears or rotors, housing, pressure relief devices, and pump driveReport a problem with this question

16. 16. A cast aluminum cylinder head has been removed and cleaned. How is the head's mating (deck) surface checked for warpage?

    • A.Pressure test the head with the valves installed and watch for leakage
    • B.Measure the head's thickness at each end with an outside micrometer and compare the two readings
    • C.Sweep each combustion chamber with a dial bore gauge
    • D.Lay a precision straightedge across the surface and measure any gap with a feeler gauge, checking lengthwise and along both diagonals✓ Answer

    Warpage is a departure from flatness, so it must be measured as the gap between the surface and a reference known to be flat, and feeler gauges read that gap directly. The checks are made lengthwise and on both diagonals because aluminum heads that have been overheated typically bow in the middle, which a single end-to-end thickness measurement would miss. If the gap exceeds the manufacturer's limit the head is resurfaced or replaced, and the resurfaced finish must meet the specified surface roughness, since MLS gaskets require a smoother finish than composite gaskets.

    Source: ASE A1 Engine Repair task list, Area B (Cylinder Head and Valve Train) — inspect cylinder head for cracks and warpage; inspect mating surface condition and finishReport a problem with this question

17. 17. A cylinder head is being installed on an engine that uses torque-to-yield (TTY) head bolts. Which procedure is correct?

    • A.Reuse the original bolts, tightening them in three equal stages with a torque wrench only
    • B.Reuse the original bolts and tighten them to one final torque value working from the outside inward
    • C.Install new bolts, tighten to final torque, then retorque them after the engine has reached operating temperature
    • D.Install new bolts and tighten them in the specified sequence to a starting torque, then turn each an additional specified number of degrees✓ Answer

    TTY bolts are deliberately tightened past their elastic limit so that they stretch permanently and hold a nearly constant clamping load; once stretched they cannot reliably produce that load again, so they are single-use and must be replaced. Final clamping force is set by rotating the fastener a specified angle after a starting torque, measured with a torque-angle gauge, and the manufacturer's tightening sequence and stages must be followed so the gasket is loaded evenly.

    Source: ASE A1 Engine Repair task list, Area B (Cylinder Head and Valve Train) — reassemble and torque cylinder head assembly and fasteners according to manufacturer's proceduresReport a problem with this question

18. 18. An engine with mechanical (solid) lifters has one burnt exhaust valve. Which condition is the MOST likely cause?

    • A.A worn camshaft lobe that reduces valve lift
    • B.Excessive valve lash (too much clearance)
    • C.A valve spring with excessive free height
    • D.Insufficient valve lash, holding the valve slightly off its seat✓ Answer

    An exhaust valve sheds most of its heat through its face into the seat and then into the coolant while it is closed. If lash is too tight the valve is held slightly open, the heat path into the seat is broken, and the valve overheats until the face erodes and burns. Too much lash instead causes valve-train noise and reduced effective lift and duration, and a worn lobe reduces lift and power without holding the valve off its seat.

    Source: ASE A1 Engine Repair task list, Area B (Cylinder Head and Valve Train) — inspect and adjust valve lash/preload; inspect valves and valve seatsReport a problem with this question

19. 19. The camshaft drive belt breaks while an interference-design engine is running at speed. What is the MOST likely result?

    • A.The camshaft and crankshaft stay in time, so the engine restarts once a new belt is installed
    • B.Pistons strike open valves, bending valves and possibly damaging pistons and guides✓ Answer
    • C.The engine keeps running at reduced power until it overheats
    • D.The engine stalls with no internal damage; only the belt needs to be replaced

    In an interference design the valve at full lift occupies part of the space the piston sweeps through, and correct valve timing is the only thing that keeps them apart. When the drive fails the camshaft stops while the crankshaft keeps turning under momentum, so pistons collide with valves that are hanging open. This is why manufacturers specify a replacement interval for the belt, and why the same failure on a non-interference (free-running) engine only stops the engine.

    Source: ASE A1 Engine Repair task list, Area B (Cylinder Head and Valve Train) — inspect and replace camshaft drive belt/chain and related components; verify valve timingReport a problem with this question

20. 20. Plastigage is being used to check connecting rod bearing oil clearance during assembly. Which statement describes correct use?

    • A.Oil the journal and the strip first so the Plastigage crushes evenly
    • B.Place a strip on the journal, torque the cap, then rotate the crankshaft one full turn before removing the cap
    • C.Measure the LENGTH of the flattened strip and compare it to the package scale
    • D.Place a strip on the clean, dry journal, install the cap and torque it to specification without rotating the crankshaft, then remove the cap and compare the flattened WIDTH to the package scale✓ Answer

    Plastigage works because a fixed volume of soft plastic crushes to a width that corresponds to the gap: the wider it spreads, the smaller the clearance. Rotating the crankshaft smears the material and destroys the reading, and oil on the journal or the strip prevents it from crushing correctly, so both surfaces must be clean and dry. Only the width is compared to the printed scale; length has no meaning.

    Source: ASE A1 Engine Repair task list, Area C (Engine Block Diagnosis and Repair) — determine main and connecting rod bearing clearances using manufacturer's proceduresReport a problem with this question

21. 21. A cylinder bore is being measured with a dial bore gauge. Which statement correctly describes how taper and out-of-round are determined?

    • A.Taper is the difference between two readings taken 90° apart at the same depth; out-of-round is the difference between the top and the bottom of the bore
    • B.Taper is the difference between readings at the top and the bottom of ring travel; out-of-round is the difference between readings taken parallel to and 90° from the crankshaft at the same depth✓ Answer
    • C.Both are checked with a precision straightedge and a feeler gauge
    • D.Both are found by subtracting piston diameter from bore diameter

    Taper is a change in diameter along the length of the bore, produced because ring pressure and abrasive wear are greatest at the top of ring travel and there is no wear below it, so it is read as top-of-travel minus bottom-of-travel. Out-of-round is a change in shape at a single depth, produced mainly by piston thrust loading, so it is read parallel to and 90° from the crankshaft at the same height. Subtracting piston diameter from bore diameter gives piston-to-wall clearance, which is a different measurement, and a straightedge and feeler gauge check flat surfaces, not bores.

    Source: ASE A1 Engine Repair task list, Area C (Engine Block Diagnosis and Repair) — clean and inspect cylinder walls/bore and measure for wear, taper, and out-of-roundReport a problem with this question

22. 22. A technician suspects excessive crankshaft end play. How is end play measured, and what does an out-of-specification reading indicate?

    • A.With Plastigage on the main journals; it indicates excessive main bearing oil clearance
    • B.With a dial bore gauge in the main bearing bores; it indicates a misaligned main bore
    • C.With a dial indicator set against the end of the crankshaft while the crank is pried fully fore and aft; it indicates a worn thrust bearing or thrust surface✓ Answer
    • D.With a feeler gauge between the connecting rod and the crank cheek; it indicates worn rod bearings

    End play is axial (front-to-back) movement of the crankshaft, so it is measured with a dial indicator on the crank snout or flange while the crankshaft is levered fully one direction and then the other; the total travel is the end play. That movement is limited by the thrust bearing or thrust flange, so a reading above specification means the thrust surface is worn — a condition that also shows up as crankshaft movement when a manual-transmission clutch pedal is applied. Plastigage and bore gauges measure radial oil clearance and bore alignment, which are different dimensions.

    Source: ASE A1 Engine Repair task list, Area C (Engine Block Diagnosis and Repair) — inspect crankshaft for end play, thrust flange condition, and journal wearReport a problem with this question

Practice questions written to the ASE Automobile & Light Truck (A-series) task lists and standard automotive service principles. ASE is a mark of the National Institute for Automotive Service Excellence; this site is not affiliated with or endorsed by ASE. Always follow the vehicle manufacturer's service information for specifications and procedures on a real repair. About the ASE tests →