I85PREP
⌘ K
ASE T1 Gasoline Engines (Medium/Heavy Truck) study materials
ASE T1 Gasoline Engines (Medium/Heavy Truck) study resources

ASE T1 Gasoline Engines (Medium/Heavy Truck) practice questions

One question at a time. Build your ASE T1 Gasoline Engines (Medium/Heavy Truck) understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1General Engine Diagnosis

A gasoline engine cranks normally but will not start. Which of these is the most useful first step in diagnosis?

  1. Check for spark at a plug wire and for fuel pressure Correct answer.
  2. Replace the ignition coil and spark plugs
  3. Drain and replace the engine oil
  4. Adjust the valve lash to specification

Explanation

A no-start complaint is diagnosed by confirming the three essentials: spark, fuel, and compression. Verifying spark and fuel pressure quickly separates an ignition fault from a fuel delivery fault before any parts are replaced.

Question 2General Engine Diagnosis

An engine with a distributor-type ignition has good spark at the coil wire but no spark at any spark plug wire. Which component is the most likely cause?

  1. The ignition coil
  2. The battery
  3. The distributor cap or rotor Correct answer.
  4. The spark plugs

Explanation

Spark reaching the coil wire proves the coil and primary circuit are producing high voltage. The distributor cap and rotor are the path that delivers that voltage to the individual plug wires, so a failure there stops spark at every plug.

Question 3General Engine Diagnosis

During a compression test on a warm engine, one cylinder reads about 60 psi while the others read 150 psi. What does this most directly indicate?

  1. A rich fuel mixture in that cylinder
  2. An ignition timing error
  3. A leaking or damaged cylinder Correct answer.
  4. A restricted exhaust system

Explanation

Compression is a mechanical sealing test; a single low cylinder points to a leak past the rings, valves, or head gasket. Fuel and ignition faults do not lower cranking compression.

Question 4General Engine Diagnosis

A wet compression test is performed by adding a small amount of oil to a low cylinder. The reading rises significantly. What does this indicate?

  1. A blown head gasket
  2. Worn piston rings Correct answer.
  3. A burned exhaust valve
  4. A cracked cylinder head

Explanation

Oil temporarily seals the gap between the rings and the cylinder wall, so a pressure increase on the wet test shows the leak is past the rings. If the reading stays low, the leak is more likely at a valve or gasket.

Question 5General Engine Diagnosis

A cylinder leakage test shows air escaping from the radiator filler neck with the radiator cap removed. Which is the most likely cause?

  1. Head gasket or cracked head Correct answer.
  2. Exhaust valve not sealing
  3. Worn piston rings
  4. Intake valve not sealing

Explanation

Air entering the cooling system during a leakage test indicates a breach between the combustion chamber and a coolant passage, typically the head gasket or a cracked casting. Valve and ring leaks vent to the intake, exhaust, or crankcase instead.

Question 6General Engine Diagnosis

An engine has a steady misfire on one cylinder and a vacuum gauge reading that fluctuates rapidly at idle. Which condition best fits these symptoms?

  1. A clogged fuel filter
  2. A leaking intake manifold gasket
  3. A faulty oxygen sensor
  4. A worn camshaft lobe or bad valve Correct answer.

Explanation

A rapid vacuum needle fluctuation combined with a steady single-cylinder misfire suggests a mechanical valve or cam problem on that cylinder. A leaking gasket usually causes a steadier low reading, and fuel or sensor faults do not produce a rhythmic vacuum fluctuation.

Question 7General Engine Diagnosis

A scan tool shows a coolant temperature sensor reading of -40 degrees F on a warm engine. What effect will this most likely have on the engine?

  1. The PCM will command a rich mixture Correct answer.
  2. The PCM will lock ignition timing at base
  3. The PCM will disable the fuel pump
  4. The PCM will command a lean mixture

Explanation

An unrealistically cold coolant reading is interpreted by the PCM as a cold engine, so it commands extra fuel enrichment. This produces a rich-running condition and can set fuel trim or sensor codes.

Question 8General Engine Diagnosis

Which condition would most likely cause an engine to crank slowly and produce a heavy, rhythmic drag on one cylinder?

  1. A faulty coolant temperature sensor
  2. Excessive carbon buildup or a hydraulic lock in one cylinder Correct answer.
  3. Advanced ignition timing on all cylinders
  4. A weak battery with clean connections

Explanation

A rhythmic drag during cranking points to unequal resistance, such as a cylinder with excessive carbon or liquid in it. A battery or timing fault would slow cranking evenly across all cylinders.

Question 9General Engine Diagnosis

An engine backfires through the intake during acceleration. Which is the most likely cause?

  1. Ignition timing too far advanced or a lean mixture Correct answer.
  2. A faulty fuel pump relay
  3. Ignition timing too far retarded
  4. A restricted air filter

Explanation

Intake backfire occurs when combustion happens while the intake valve is still open, which is caused by over-advanced timing or a lean condition that burns slowly. Retarded timing tends to produce exhaust afterfire instead.

Question 10General Engine Diagnosis

A technician observes blue-gray smoke from the tailpipe that is worst after idling and on deceleration. What does this indicate?

  1. Engine oil entering the combustion chamber Correct answer.
  2. Coolant entering the combustion chamber
  3. An excessively rich fuel mixture
  4. A restricted catalytic converter

Explanation

Blue-gray smoke is oil smoke, and it worsening after idle and during deceleration points to valve guides or seals. Coolant produces white smoke and rich mixture produces black smoke.

Question 11General Engine Diagnosis

An engine runs rough only at idle and smooths out at higher speed. A vacuum gauge reads low and steady, and a propane test at the intake manifold raises engine speed. What is the most likely cause?

  1. Worn piston rings
  2. A weak ignition coil
  3. A vacuum leak Correct answer.
  4. A clogged fuel injector

Explanation

Adding propane enriches the mixture and raising engine speed confirms extra air is entering unmetered, which is a vacuum leak. A leak has the greatest effect at idle when manifold vacuum is highest.

Question 12General Engine Diagnosis

Which test best determines whether an engine's rough idle is caused by an ignition misfire or a fuel delivery problem on a specific cylinder?

  1. An oil pressure test
  2. A charging system voltage test
  3. A cylinder balance or power contribution test Correct answer.
  4. A cooling system pressure test

Explanation

A cylinder balance test disables or measures each cylinder's contribution to identify the weak cylinder. Once identified, spark and fuel can be checked at that cylinder to isolate the cause.

Question 13General Engine Diagnosis

A vehicle has a P0300 random misfire code. Which condition is most likely to produce a random misfire rather than a single-cylinder misfire?

  1. A single failed injector
  2. A broken valve spring on one cylinder
  3. A vacuum leak affecting the whole intake Correct answer.
  4. A single fouled spark plug

Explanation

A P0300 indicates misfire across multiple cylinders, which points to a common cause such as a vacuum leak, low fuel pressure, or ignition system problem. Single-cylinder faults set codes for that specific cylinder.

Question 14General Engine Diagnosis

An engine has a rough idle and a hissing noise near the intake manifold that changes with engine speed. Which is the most likely cause?

  1. A faulty thermostat
  2. A clogged PCV valve
  3. A leaking intake manifold gasket Correct answer.
  4. A worn timing chain

Explanation

A hissing noise near the intake that varies with speed is characteristic of a vacuum leak at a gasket or hose. A leaking intake gasket admits unmetered air and disrupts idle quality.

Question 15General Engine Diagnosis

A compression test shows all cylinders low but nearly equal, and the engine consumes oil and lacks power. What is the most likely cause?

  1. Worn piston rings and cylinder walls Correct answer.
  2. A leaking head gasket
  3. A jumped timing chain
  4. A faulty ignition module

Explanation

Uniformly low compression across all cylinders with oil consumption indicates general mechanical wear, most often ring and cylinder wall wear. A head gasket or timing fault usually affects compression unevenly or not at all.

Question 16General Engine Diagnosis

Which tool is used to measure the pressure in the cooling system while checking for a combustion gas leak into the coolant?

  1. A cooling system pressure tester Correct answer.
  2. A compression gauge
  3. A vacuum gauge
  4. A timing light

Explanation

A cooling system pressure tester pressurizes the system to locate external leaks and, combined with combustion gas detection, can help confirm an internal leak. Compression and vacuum gauges measure different parameters.

Question 17General Engine Diagnosis

An engine overheats only at highway speed but runs at normal temperature in city driving. Which is the most likely cause?

  1. A sticking thermostat
  2. A restricted radiator or airflow problem Correct answer.
  3. A loose fan belt
  4. A faulty coolant temperature sensor

Explanation

Overheating at highway speed with normal city temperatures suggests the cooling system cannot dissipate heat under sustained load, such as a restricted radiator or poor airflow. A thermostat or belt problem typically causes overheating in all conditions.

Question 18General Engine Diagnosis

A scan tool shows long-term fuel trim at plus 25 percent on both banks. What does this indicate?

  1. The PCM is reducing fuel because the mixture is rich
  2. The oxygen sensor is disconnected
  3. The PCM is adding fuel because the mixture is lean Correct answer.
  4. The engine is misfiring on one cylinder

Explanation

Positive fuel trim means the PCM is lengthening injector pulse width to compensate for a lean condition. A large positive trim on both banks points to a common cause such as a vacuum leak or low fuel pressure.

Question 19General Engine Diagnosis

An engine cranks but has no spark, and the scan tool shows no rpm signal during cranking. Which component should be checked first?

  1. The fuel pump
  2. The spark plugs
  3. The crankshaft position sensor Correct answer.
  4. The throttle position sensor

Explanation

The PCM needs a crankshaft position signal to calculate rpm and trigger ignition. No rpm during cranking points to the crank sensor or its circuit before other ignition parts are investigated.

Question 20General Engine Diagnosis

A timing light shows that ignition timing does not advance when engine speed increases. Which is the most likely cause?

  1. A failed ignition control module or PCM advance circuit Correct answer.
  2. A faulty ignition coil
  3. Worn spark plug wires
  4. A disconnected or faulty knock sensor

Explanation

Timing advance is commanded electronically by the ignition control module or PCM based on speed and load. If timing stays fixed, the advance control circuit or module is suspect.

Question 21General Engine Diagnosis

Which condition causes an engine to ping or knock under acceleration and is confirmed by retarded timing and the use of low-octane fuel?

  1. A faulty EGR valve stuck open
  2. Detonation from fuel octane too low Correct answer.
  3. Pre-ignition from excessive carbon
  4. A lean fuel mixture at idle

Explanation

Detonation is the abnormal, rapid burning of the end gas and is aggravated by low-octane fuel, high load, and advanced timing. Using the specified octane fuel and verifying timing are the first corrective steps.

Question 22General Engine Diagnosis

An engine has a dead miss on one cylinder. Swapping the spark plug and wire with another cylinder does not change the misfire location. What should be checked next?

  1. The coolant temperature sensor
  2. The fuel injector and compression for that cylinder Correct answer.
  3. The battery and charging system
  4. The exhaust system

Explanation

If the miss stays on the same cylinder after ignition parts are swapped, the fault is not in the plug or wire. The next checks are fuel delivery and mechanical condition for that cylinder.

Question 23General Engine Diagnosis

A vacuum gauge connected to the intake manifold reads steady at about 10 in-Hg at idle on a stock engine. What does this most likely indicate?

  1. A worn distributor gear
  2. A restricted exhaust
  3. A large vacuum leak or late valve timing Correct answer.
  4. A normal reading

Explanation

A healthy stock engine typically shows about 17 to 22 in-Hg at idle. A steady low reading points to a large vacuum leak or retarded valve timing that reduces the manifold vacuum.

Question 24General Engine Diagnosis

Which symptom most directly suggests a failed head gasket between two adjacent cylinders?

  1. The oil pressure warning light stays on
  2. All cylinders show high compression
  3. Two adjacent cylinders both show low compression and the engine overheats Correct answer.
  4. The engine idles smoothly but lacks high-speed power

Explanation

A head gasket breach between two cylinders allows compression to escape from one into the other, lowering compression on both. It commonly allows combustion gas into the cooling system, causing overheating.

Question 25General Engine Diagnosis

A technician performs a running compression test and finds one cylinder has much lower running compression than the others. Which additional test best confirms a valve sealing problem on that cylinder?

  1. An oil pressure test
  2. A cylinder leakage test with the piston at TDC on compression Correct answer.
  3. A charging system test
  4. A fuel pressure test

Explanation

A cylinder leakage test at TDC on the compression stroke measures where pressure escapes and confirms whether a valve, ring, or gasket is at fault. Listening at the intake or exhaust identifies the leaking valve.

Question 26General Engine Diagnosis

A gasoline engine cranks but will not start. A spark tester shows strong spark at every cylinder, and the fuel pump is supplying normal pressure. Which test should be performed next to confirm whether the injectors are being pulsed?

  1. Connect a noid light to an injector connector and crank the engine Correct answer.
  2. Check the resistance of each spark plug wire
  3. Perform a cylinder leakage test on each cylinder
  4. Measure fuel pressure at the rail with the engine off

Explanation

A noid light substitutes for an injector and flashes when the PCM pulses the circuit, which separates a control-side fault from a fuel delivery fault. With spark and fuel pressure already confirmed, verifying injector pulse is the next logical step in the no-start diagnosis.

Question 27General Engine Diagnosis

During a cylinder balance test, disconnecting one injector causes no change in engine rpm or smoothness while all others cause a noticeable drop. Which conclusion is best supported?

  1. That cylinder is contributing little or nothing to power output Correct answer.
  2. The engine is operating within normal balance limits
  3. The ignition coil for that cylinder is firing normally
  4. The fuel pump is delivering excessive pressure

Explanation

A cylinder that produces no rpm drop when its fuel is cut is not contributing to power, pointing to a fault specific to that cylinder. The other cylinders dropping normally shows the test setup and overall fuel delivery are sound.

Question 28General Engine Diagnosis

A scan tool on an engine with a rough idle shows short-term fuel trim oscillating between plus 20 percent and minus 15 percent on one bank only. Which condition best fits this pattern?

  1. A restricted exhaust system downstream of the catalytic converter
  2. A clogged fuel filter affecting both banks equally
  3. A thermostat stuck open causing low operating temperature
  4. An intermittent lean condition on that bank, such as a leaking intake gasket Correct answer.

Explanation

Wide swings in short-term trim on a single bank indicate the PCM is chasing an intermittent air or fuel imbalance limited to that bank. An intake leak that opens and closes with vibration or heat is a common cause of this pattern.

Question 29General Engine Diagnosis

An engine has a consistent low-pitched knock that is loudest at the rear of the engine, is present at hot idle, and changes little with load. Which is the most likely cause?

  1. An exhaust manifold gasket leak
  2. Detonation from low-octane fuel
  3. A loose accessory drive belt
  4. A worn main or rod bearing Correct answer.

Explanation

Bearing knock is a deep, dull sound heard at hot idle and is less load-sensitive than detonation. Detonation is a sharper rattle heard under load and typically clears when load is removed.

Question 30General Engine Diagnosis

A wet compression test raises compression on a cylinder from 90 psi to 140 psi, while dry compression on the other cylinders is 150 to 160 psi. Which additional test best distinguishes worn rings from worn valve guides or seals on that cylinder?

  1. A fuel pressure drop test at the rail
  2. A running compression test at idle speed only
  3. A vacuum gauge reading taken at the intake manifold
  4. A cylinder leakage test with the engine warmed and the piston at top dead center on compression Correct answer.

Explanation

A wet test rising sharply shows the compression loss is past the rings or valve sealing, and a leakage test with air applied localizes where the air escapes. Air heard at the crankcase indicates rings, while air at the intake or exhaust indicates valves.

Question 31Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A diesel technician finds a valve stem height that is below the minimum specification after a valve job. Which of the following is the most likely cause?

  1. The valve spring installed height is too tall.
  2. The valve seat was ground too deep into the head. Correct answer.
  3. The valve guide clearance is excessive.
  4. The rocker arm adjustment is backed off.

Explanation

Valve stem height is set by the relationship between the valve face and the seat in the head. Grinding the seat too deeply sinks the valve and pulls the stem tip below the minimum height. Guide clearance, spring height, and rocker adjustment do not change the stem tip's physical position relative to the head.

Question 32Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

During a cylinder head inspection, a technician measures valve recession and finds it is within specification. What does this measurement confirm?

  1. The valve guide bore is round within tolerance.
  2. The valve face sits at the correct depth relative to the head surface. Correct answer.
  3. The valve spring has the correct free length.
  4. The camshaft lobe lift is within specification.

Explanation

Valve recession is the distance the valve face sits below (or above) the cylinder head fire deck when seated. It directly reflects how deep the valve sits in the head after seat work. Spring length, guide roundness, and lobe lift are unrelated measurements.

Question 33Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A pushrod engine has excessive valve lash on one intake valve after the head was reinstalled. Which of the following is the most likely cause?

  1. The valve guide was replaced with an oversized guide.
  2. The valve stem tip was ground too short during the valve job. Correct answer.
  3. The valve seal was installed upside down.
  4. The head gasket is thicker than the original.

Explanation

Excessive lash means the valvetrain has too much clearance between the rocker and the valve stem tip. Grinding the stem tip short removes material that the rocker needs to contact, increasing lash. Guide size, seal orientation, and gasket thickness do not directly create excess lash at one valve.

Question 34Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A technician is checking valve spring installed height. Which of the following best describes what is being measured?

  1. The distance the valve travels from closed to fully open.
  2. The free length of the spring before installation.
  3. The distance from the spring seat to the retainer with the valve closed. Correct answer.
  4. The distance from the valve tip to the spring seat.

Explanation

Installed height is measured with the valve closed, from the spring seat (head or shim) to the underside of the retainer. It determines the spring's preload and must match specifications. Valve lift, free length, and stem protrusion are different measurements.

Question 35Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A cylinder head shows a burned exhaust valve on one cylinder. Which of the following conditions is the most likely root cause?

  1. A collapsed lifter on the intake side
  2. A worn valve guide seal allowing oil past the stem
  3. Excessive valve lash holding the valve off its seat
  4. Insufficient valve lash preventing full closure Correct answer.

Explanation

A valve must seat fully to transfer heat into the head. Insufficient lash (or a valve held slightly open) prevents full seating, so the valve overheats and can burn. Excessive lash would cause noise and reduced lift but not typically a burned valve.

Question 36Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

Which of the following is the correct procedure for checking valve guide wear with a dial indicator?

  1. Measure stem diameter at the top of the stem only.
  2. Measure side play of the valve head with the valve lifted slightly off its seat. Correct answer.
  3. Measure camshaft lobe height across the base circle.
  4. Measure spring free length and compare to specification.

Explanation

Guide wear is checked by lifting the valve slightly off its seat and measuring side-to-side movement of the stem or valve head with a dial indicator. Comparing that reading to specification reveals guide clearance. Measuring only the stem top, spring length, or lobe height does not assess guide clearance.

Question 37Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A technician observes that the valve spring retainer is contacting the valve guide boss at full lift. Which of the following is the most appropriate correction?

  1. Increase valve lash to reduce lift.
  2. Reduce spring installed height with additional shims.
  3. Replace the valve with a longer stem.
  4. Machine the guide boss for additional clearance or reduce retainer thickness. Correct answer.

Explanation

Retainer-to-guide clearance must be verified at full lift, especially with high-lift cams. The fix is to machine the guide boss for clearance or use a thinner retainer. Adjusting lash or shimming the spring does not change the physical interference.

Question 38Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A valve seat that is too wide will most likely cause which of the following conditions?

  1. Camshaft lobe scuffing
  2. Valve spring surge at high RPM
  3. Poor heat transfer and possible valve burning Correct answer.
  4. Excessive oil consumption past the guide

Explanation

A wide seat reduces seating pressure per unit area, which can prevent the valve from sealing tightly and transferring heat efficiently, leading to burning. Seat width does not affect guide oil control, spring surge, or cam lobe wear.

Question 39Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

When performing a valve seat concentricity check with a dial indicator on the valve stem, what is being verified?

  1. That the valve seat is centered on the guide bore Correct answer.
  2. That the valve spring is square
  3. That the rocker arm geometry is correct
  4. That the camshaft bearing journals are round

Explanation

Seat concentricity is checked by rotating the valve in the guide with an indicator on the valve face or seat. Runout indicates the seat is not centered on the guide bore, which causes poor sealing. Spring squareness, rocker geometry, and cam journal roundness are separate checks.

Question 40Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A technician finds a cracked cylinder head between the valve seats. Which of the following is the most common cause of this type of crack?

  1. Too much valve lash
  2. Excessive valve spring pressure
  3. Incorrect rocker arm adjustment
  4. Overheating and thermal stress Correct answer.

Explanation

Cracks between valve seats typically result from thermal stress caused by overheating or uneven cooling. The metal expands and contracts unevenly, and the narrow area between the seats is a stress riser. Spring pressure, lash, and rocker adjustment do not typically produce this crack pattern.

Question 41Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A camshaft lobe shows severe wear on the nose with a flattened profile. Which of the following is the most likely cause?

  1. Excessive valve guide clearance
  2. Improperly torqued head bolts
  3. A leaking head gasket
  4. Incorrect valve lash and inadequate lubrication during break-in Correct answer.

Explanation

Lobe wear is commonly caused by insufficient lubrication, incorrect break-in procedures, or excessive lash that increases contact stress. The nose of the lobe sees the highest load and wears first. Guide clearance, head gasket leaks, and head bolt torque do not directly cause lobe scuffing.

Question 42Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

When degreeing a camshaft, the technician is primarily verifying which of the following?

  1. The rocker arm ratio
  2. The camshaft's timing events relative to the crankshaft Correct answer.
  3. The valve spring installed height
  4. The valve guide clearance

Explanation

Degreeing a cam confirms that the intake and exhaust lobe centerlines and opening/closing events occur at the correct crankshaft positions. It uses a degree wheel and dial indicator on the lifter. Spring height, guide clearance, and rocker ratio are separate measurements.

Question 43Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A pushrod is found bent in a running engine. Which of the following is the most likely cause?

  1. Excessive valve spring installed height
  2. A leaking exhaust manifold gasket
  3. A worn valve guide seal
  4. Valve-to-piston contact due to insufficient clearance Correct answer.

Explanation

A bent pushrod usually results from the valvetrain being forced against a stop, such as a valve contacting the piston or a valve sticking in the guide. The pushrod buckles under the load. Seals, spring height, and exhaust leaks do not bend pushrods.

Question 44Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A hydraulic lifter in a pushrod engine is noisy at startup and quiets after warm-up. Which of the following is the most likely cause?

  1. Excessive valve spring pressure
  2. Too little valve lash
  3. A worn camshaft bearing
  4. A lifter that is bleeding down and losing preload Correct answer.

Explanation

A hydraulic lifter that bleeds down overnight loses its preload and clatters until oil pressure refills it. This is a common cause of cold-start noise that fades as the engine warms. Spring pressure, lash, and cam bearings do not produce that specific symptom pattern.

Question 45Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A technician is measuring valve spring pressure with a spring tester. The spring is shorter than specification at the specified installed height. Which of the following is the correct interpretation?

  1. The spring has lost tension and should be replaced. Correct answer.
  2. The spring has the wrong wire diameter.
  3. The spring is too stiff and should be shimmed.
  4. The spring is correct and can be reused.

Explanation

A spring that does not reach specified pressure at the specified height has taken a set and lost tension. It should be replaced rather than shimmed. Shimming a weak spring increases preload but does not restore the lost rate.

Question 46Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A cylinder head has been resurfaced, and the technician now finds the valve stem heights are below specification. Which of the following is the most appropriate repair?

  1. Add shims under the valve springs
  2. Machine the head further to raise the stems
  3. Install longer valves or valve seat inserts to restore geometry Correct answer.
  4. Increase valve lash at the rocker

Explanation

Resurfacing the head lowers the deck relative to the valve seats, which can change stem height. The correct repair restores the valve-to-head geometry, typically with longer valves or new seat inserts. Shimming springs, adjusting lash, or removing more material does not correct stem height.

Question 47Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

Which of the following best describes the purpose of a valve rotator on an exhaust valve?

  1. To reduce valve spring pressure
  2. To rotate the valve so it wears and heats evenly Correct answer.
  3. To seal the valve guide from oil
  4. To increase valve lift at high RPM

Explanation

A valve rotator turns the valve slightly each time it opens, distributing wear and heat around the valve face and seat. This extends valve life and reduces the chance of localized burning. It does not change lift, spring pressure, or guide sealing.

Question 48Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A technician is checking rocker arm geometry and finds the contact pattern is biased toward the exhaust side of the valve tip. Which of the following is the most likely cause?

  1. The valve guide clearance is excessive
  2. The valve spring is weak
  3. The head gasket is leaking
  4. The rocker arm pedestal height or pushrod length is incorrect Correct answer.

Explanation

Rocker geometry is set by pedestal height, pushrod length, and rocker design. An off-center or narrow contact pattern indicates the geometry is wrong and should be corrected with the proper pushrod length or pedestal shimming. Spring weakness, guide clearance, and gasket leaks do not shift the contact pattern.

Question 49Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A technician finds excessive side-to-side movement of the valve in the guide when the valve is partially open. Which of the following is the most likely consequence if left unrepaired?

  1. Improved valve sealing
  2. Reduced camshaft lobe wear
  3. Increased valve spring pressure
  4. Uneven valve seat wear and possible valve breakage Correct answer.

Explanation

Excess guide clearance allows the valve to wobble, which causes uneven seat contact, poor heat transfer, and concentrated stress that can lead to valve breakage. It does not improve sealing, change spring pressure, or reduce lobe wear.

Question 50Cylinder Head, Valve Train, and Camshaft Diagnosis and Repair

A technician is inspecting a cylinder head for warpage using a straightedge and feeler gauge. Which of the following is the correct method?

  1. Measure only the combustion chamber side
  2. Measure across the head in one direction only
  3. Measure only the manifold surfaces
  4. Measure diagonally, longitudinally, and laterally at multiple points Correct answer.

Explanation

Warpage checks require the straightedge to be placed in multiple directions (diagonal, longitudinal, and lateral) across the deck surface, with a feeler gauge at each location. A single direction can miss a warp along another axis. Checking only the chamber side or manifold surfaces does not verify deck flatness.