22 Engine, Cooling, Fuel & Emissions Parts Practice Questions & Answers
Every Engine, Cooling, Fuel & Emissions Parts practice question from the ASE P2 Parts Specialist Practice Test, with the correct answer and a short explanation.
Start practice test →1. A customer is replacing a stretched timing chain on an overhead-valve engine. When the counter person pulls a "timing set," what does that package normally contain?
- A.The chain together with the lifters, pushrods and rocker arms
- B.The chain together with the water pump, drive belt and belt tensioner
- C.The chain together with the matching camshaft and crankshaft sprockets✓ Answer
- D.The chain together with the front cover gasket, seal and cover bolts
A timing set is sold as a matched wear group: the chain and both sprockets wear together, so installing a new chain against worn sprocket teeth lets the new chain elongate again very quickly. Gaskets and seals are a separate timing gasket set, and overhead-cam kits may add guides and a tensioner.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Engine Mechanical Parts (identify major components and related items)Report a problem with this question
2. Note: this question is an EXCEPT question. All of the following are true when selling a replacement timing belt EXCEPT:
- A.It stretches gradually in service, so a slightly longer belt is acceptable✓ Answer
- B.It must have the same tooth profile and the same width as the original
- C.It is often sold in a kit that adds the idler and tensioner pulleys
- D.It must have the same tooth count and the same overall length as the original
A timing belt carries inextensible reinforcing cords, so it does not stretch in service the way a worn chain elongates; it fails by cracking, glazing, tooth loss or backing separation. Because the belt cannot take up slack, the replacement must duplicate the original tooth count, length, tooth profile and width exactly.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Engine Mechanical Parts (timing belt use, maintenance and installation information)Report a problem with this question
3. A machine shop has reground a crankshaft, and the customer asks for undersize bearings. What does the undersize designation tell the counter person about those bearings?
- A.The shells are narrower, to fit a block whose bearing bores have been enlarged
- B.The shells are thinner, to restore clearance on journals machined above standard size
- C.The shells are wider, to fit a crankshaft needing added thrust surface clearance
- D.The shells are thicker, to restore clearance on journals machined below standard size✓ Answer
The undersize figure describes the crankshaft journal, not the bearing shell. Grinding removes metal from the journal, so the replacement shell must be correspondingly thicker to bring oil clearance back to specification; the counter person must know how far the journals were cut before pulling the parts.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Engine Mechanical Parts (engine bearing sizing for reground journals)Report a problem with this question
4. A customer is buying a new oil pump during an engine overhaul. Which related item should the counter person recommend along with the pump?
- A.A new pickup tube and screen, because the old screen holds debris✓ Answer
- B.A new oil pressure sending unit, because the pump cannot build pressure without it
- C.A heavier viscosity engine oil, because a new pump seats faster on thicker oil
- D.A new engine oil cooler, because a rebuilt engine runs hotter than the original one
The pickup screen is full of the debris that wore out the old pump, and the tube-to-pump joint or seal is disturbed whenever the tube is pulled. A restricted screen starves the new pump and a leaking joint lets it draw air, so the pickup goes on the ticket with every pump.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Engine Mechanical Parts (oil pump and related items)Report a problem with this question
5. A customer needs a replacement assembly that includes the block with the crankshaft, connecting rods and pistons installed, but no cylinder head. That assembly is cataloged as a:
- A.Bare block
- B.Short block✓ Answer
- C.Long block
- D.Complete engine
A short block is the assembled bottom end only. A long block adds the cylinder head or heads and the valvetrain, a complete engine adds bolt-on accessories such as the intake, oil pan and often the water pump, and a bare block is a machined casting with nothing installed.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Engine Mechanical Parts (engine assembly types offered for sale)Report a problem with this question
6. Parts specialist A says the water pump draws coolant out of the radiator and pushes it into the engine block. Parts specialist B says a replacement pump must match the original drive type and impeller rotation. Who is right?
- A.Both A and B✓ Answer
- B.B only
- C.Neither A nor B
- D.A only
The lower radiator hose feeds the pump inlet and the pump outlet discharges into the block or timing cover, so flow runs from radiator to engine. Some engines are driven on the flat back side of a serpentine belt and use a reverse-rotation pump, so drive type and impeller rotation must be matched when the part is selected.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Cooling Systems (water pump function and component identification)Report a problem with this question
7. Note: this question is an EXCEPT question. All of the following are true of a cooling system pressure cap EXCEPT:
- A.It lowers the freezing point of the coolant by holding the system under pressure✓ Answer
- B.It raises the boiling point of the coolant by holding the system under pressure
- C.It may be mounted on a pressurized surge tank rather than on the radiator itself
- D.It must be replaced with a cap carrying the same pressure rating as the original
Pressure only raises the boiling point, roughly a few degrees for each pound of pressure the cap holds. Freeze protection comes from the glycol concentration in the coolant, so a cap can never change the freezing point, and a replacement cap must carry the rating the system was designed around.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Cooling Systems (pressure cap function and rating)Report a problem with this question
8. Parts specialist A says a replacement thermostat must carry the temperature rating the manufacturer specifies for that engine. Parts specialist B says fitting a colder-rated thermostat to a computer-controlled engine adds a safety margin against overheating. Who is right?
- A.Both A and B
- B.A only✓ Answer
- C.B only
- D.Neither A nor B
The engine controller is calibrated around the specified operating temperature and uses coolant temperature to decide when to leave open loop, so a colder thermostat leaves the engine running rich, hurts economy and heater output, and does nothing to fix the real cause of overheating. Sell the specified rating, plus the housing gasket the job needs.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Cooling Systems (thermostat function and replacement temperature rating)Report a problem with this question
9. A customer wants a gallon of coolant to top off a late-model engine and says, "mine is orange, so just give me orange." The best counter practice is to:
- A.Supply plain distilled water, because topping off a system never changes its freeze protection
- B.Supply conventional green coolant, because it is compatible with every cooling system in service
- C.Supply coolant meeting the manufacturer's specification, because dye color is not chemistry✓ Answer
- D.Supply any orange coolant, because the dye color identifies extended-life organic acid chemistry
Dye is chosen by whoever packages the product, not by any standard, and conventional, organic acid and hybrid coolants are all sold in overlapping colors. Only the vehicle manufacturer's specification identifies the right chemistry, and mixing incompatible chemistries can drop out of solution and reduce corrosion protection.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Cooling Systems (antifreeze types and compatibility with the OEM specification)Report a problem with this question
10. A customer needs an electric in-tank fuel pump for a port injected engine. Which requirement governs the counter person's selection?
- A.The replacement must use the original pump design, though its pressure and volume ratings may differ
- B.The replacement must draw the same current, whatever pressure and volume output it delivers
- C.The replacement must come from the same tank capacity group, whatever pressure output it delivers
- D.The replacement must meet the original pressure and volume ratings, though its pump design may differ✓ Answer
The engine controller meters fuel by injector pulse width against a known rail pressure, so the pump must deliver the specified pressure and the specified volume at that pressure. Turbine, gerotor, roller vane and vane designs all satisfy the application as long as those ratings are met.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Fuel Systems (fuel pump pressure and volume ratings)Report a problem with this question
11. An in-tank fuel pump module is being replaced. Which related item should always go out with the pump?
- A.A new fuel pressure regulator, along with a check of the rail for leaks
- B.A new rail crossover hose, along with a check of the injectors for varnish
- C.A new fuel filler cap, along with a check of the filler neck for corrosion
- D.A new pump inlet strainer, along with a check of the tank for debris✓ Answer
The strainer is the pump's only protection, and the debris that killed the old pump is still lying in the tank. A reused sock passes that debris into the new pump or restricts flow, and since the fuel cools and lubricates the pump, restricted flow shortens its life immediately.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Fuel Systems (fuel pump related items: strainer and fuel tank condition)Report a problem with this question
12. Parts specialist A says a speed-density fuel injection system uses a mass airflow sensor to measure the air entering the engine. Parts specialist B says a mass airflow sensor's signal is used by the engine controller to set the air/fuel mixture. Who is right?
- A.Neither A nor B
- B.A only
- C.B only✓ Answer
- D.Both A and B
A speed-density system has no mass airflow sensor at all: it calculates airflow from manifold pressure, engine speed, air temperature and throttle position. Where a mass airflow sensor is fitted, it sits between the air filter and the throttle body and its signal is a primary input for fuel metering, so only B is correct.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Fuel Systems (speed-density and mass airflow fuel injection systems)Report a problem with this question
13. Parts specialist A says low-pressure hose sold for carbureted fuel lines may be used on a port injected engine if it is double clamped. Parts specialist B says heater hose is an acceptable substitute for a cracked PCV hose. Who is right?
- A.Both A and B
- B.B only
- C.Neither A nor B✓ Answer
- D.A only
Fuel injection runs at pressures far above what carbureted-service hose is rated for, so only hose marked for fuel injection may be used, and clamping does not raise a hose's pressure rating. Heater hose is not built to resist oil and crankcase vapor and will soften or collapse, so PCV plumbing requires hose sold for that service.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Miscellaneous (hose and tubing types, proper application and usage)Report a problem with this question
14. How do the fuel delivery parts of a gasoline direct injection engine differ from those of a port fuel injected engine?
- A.It deletes the in-tank pump and relies on one high pressure pump mounted at the fuel rail
- B.It adds an engine-driven high pressure pump and injectors that spray into the combustion chamber✓ Answer
- C.It replaces the individual injectors with one or two injectors mounted in the throttle body
- D.It keeps the same rail pressure but moves each injector to the port ahead of the intake valve
Direct injection keeps the low pressure in-tank pump, which feeds a camshaft-driven high pressure pump supplying a high pressure rail and injectors that spray into the cylinder. The throttle body answer describes older throttle body injection, and the port answer describes the port injected system being compared.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Fuel Systems (fuel delivery components of throttle body, port and direct injection systems)Report a problem with this question
15. Listed from the engine rearward, what is the normal order of parts in a single exhaust system on a V8?
- A.Exhaust manifolds, Y-pipe, catalytic converter, intermediate pipe, muffler, tailpipe✓ Answer
- B.Exhaust manifolds, muffler, Y-pipe, catalytic converter, intermediate pipe, tailpipe
- C.Exhaust manifolds, Y-pipe, muffler, intermediate pipe, catalytic converter, tailpipe
- D.Exhaust manifolds, catalytic converter, Y-pipe, muffler, intermediate pipe, tailpipe
On a V engine with a single exhaust the head pipe is a Y-pipe that joins both banks ahead of the converter, and the converter sits close to the engine so it reaches light-off temperature quickly. Sound control comes last, so the muffler and any resonator follow the converter, with the tailpipe at the rear.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Exhaust Systems (identification and arrangement of exhaust components)Report a problem with this question
16. What distinguishes a direct-fit replacement muffler from a universal muffler?
- A.The direct-fit unit is sold with added shell coatings, so it outlasts every universal unit made
- B.The direct-fit unit covers many applications, so its inlet must be sized during installation
- C.The direct-fit unit duplicates the original's shape and pipe positions, so no adapters are needed✓ Answer
- D.The direct-fit unit uses a straight-through core, so it lowers backpressure more than the original
Direct-fit parts are built to the original geometry, including inlet and outlet diameters, offsets and hanger locations, so they bolt or clamp up like the factory piece. A universal muffler covers many applications but usually needs pipe cutting or adapters, while flow design, shell coating and product grade are separate choices from fitment.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Exhaust Systems (direct-fit, universal and performance replacement parts)Report a problem with this question
17. A customer replacing a rusted muffler asks why the counter person is adding new clamps, hangers and a flange gasket to the ticket. The best answer is that:
- A.Exhaust hardware is sold only in kits, so the clamps and gaskets cannot be left off the ticket
- B.New clamps and gaskets are needed only when the shop welds the joints instead of clamping them
- C.Clamps and gaskets carry the exhaust warranty, so the muffler is not covered if they are reused
- D.Heat cycling and corrosion distort exhaust hardware and crush gaskets, so used ones leak✓ Answer
Exhaust fasteners live through repeated heating and cooling in a corrosive, wet environment, which stretches and seizes them and permanently deforms the gasket that was crushed at the last assembly. Reused hardware leaks, and an exhaust leak can let carbon monoxide reach the passenger compartment, so the related items belong on every exhaust ticket.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Exhaust Systems (related items: clamps, hangers, gaskets and fasteners)Report a problem with this question
18. A vehicle needs an oxygen sensor for the position behind the catalytic converter. Why can the counter person not simply supply the sensor listed for the position ahead of the converter?
- A.The downstream position uses an unheated sensor, so only the upstream sensor needs power
- B.Both positions use the same sensor, so either part may be supplied if the harness will reach
- C.The downstream position measures fuel trim, so its sensor is always a wide-band air/fuel element
- D.The two positions use different calibrations and connectors, so the sensors are not interchangeable✓ Answer
The upstream sensor is a fuel-control device, often a wide-band air/fuel ratio sensor, while the downstream sensor is a catalyst-monitor device; they carry different part numbers, calibrations, harness lengths and connectors. Catalog the sensor by its exact position, and offer anti-seize rated for oxygen sensors or a thread chaser for the corroded bung.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Emissions Control Systems (oxygen and air/fuel ratio sensors, upstream and downstream locations)Report a problem with this question
19. A customer asks the counter person what the EGR valve on his engine actually does. Which statement is correct?
- A.It meters crankcase blowby into the intake charge, keeping vapor and moisture out of the oil
- B.It meters exhaust into the intake charge, lowering peak combustion temperature and NOx✓ Answer
- C.It meters fuel tank vapor into the intake charge, keeping that vapor out of the atmosphere
- D.It meters fresh air into the exhaust stream, helping the converter finish burning HC and CO
Oxides of nitrogen form when combustion temperature climbs, so recirculating inert exhaust dilutes the intake charge, lowers peak combustion temperature and cuts NOx, while also reducing the tendency to detonate. The other three answers describe secondary air injection, the PCV system and the evaporative system.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Emissions Control Systems (EGR system function in NOx reduction)Report a problem with this question
20. Under the federal emission warranty, a longer coverage period applies to a short list of major emission control components. Which group is on that list?
- A.The catalytic converter, the oxygen sensors, and the evaporative system charcoal canister
- B.The catalytic converter, the engine control unit, and the onboard diagnostic device✓ Answer
- C.The exhaust manifold, the electronic engine control unit, and the fuel injectors
- D.The EGR valve, the PCV valve, and the evaporative system purge solenoid
Federal law splits the vehicle emission warranty into a shorter general period that covers emission-related parts broadly and a longer period limited to the specified major components: the catalytic converter, the electronic emission control unit, and the onboard diagnostic device. Sensors, valves and canisters fall under the shorter general coverage, and this vehicle warranty is separate from the warranty an aftermarket converter itself carries.
Source: Clean Air Act emission warranty provisions, as summarized in U.S. EPA guidance on emission control system warranty coverage for vehicle ownersReport a problem with this question
21. A customer's catalytic converter is present and working, but he wants to buy an aftermarket converter because it is cheaper and louder than the original. The counter person should:
- A.Sell it, because any converter carrying a federal label may be installed on any vehicle at any time
- B.Offer a used salvage yard converter instead, because used units are exempt from the replacement rules
- C.Decline, because an aftermarket converter may be sold for installation only where a legitimate need exists✓ Answer
- D.Sell it, because the customer's signature on the invoice transfers the responsibility to the vehicle owner
Federal policy allows an aftermarket converter to be installed only when the original is missing, when an inspection program has determined that replacement is needed, or when the vehicle is beyond the original converter warranty and a documented legitimate need exists. A functioning converter may not be replaced for sound or price, an untested unlabeled salvage converter may not be sold for installation, and no customer signature makes any of that legal.
Source: U.S. EPA policy on the sale and installation of aftermarket catalytic converters (conditions for replacement and installer duties)Report a problem with this question
22. An OBD II system has reported a small leak in the evaporative emission control system. Which part should the counter person suggest inspecting and replacing first?
- A.The fuel tank pressure sensor
- B.The evaporative system charcoal canister
- C.The fuel filler cap and its gasket✓ Answer
- D.The canister purge solenoid valve
The evaporative system is a sealed circuit that the controller tests by applying pressure or vacuum, and the filler cap is the only seal the driver opens routinely, so a loose, damaged or missing cap is by far the most common cause of a small leak report. It is also the least expensive part in the circuit, which makes it the logical first item to sell.
Source: ASE P2 Automobile Parts Specialist Study Guide — Vehicle Systems Knowledge, Emissions Control Systems (evaporative emission control components and OBD II leak monitoring)Report a problem with this question
Practice questions written to the ASE P2 Automobile Parts Specialist task list and standard parts-distribution practice. ASE is a mark of the National Institute for Automotive Service Excellence; this site is not affiliated with or endorsed by ASE. Part numbers, prices, warranty and return terms, and vehicle-specific applications are deliberately left out because they vary by supplier and change constantly — always confirm an application in your own current catalog and your employer's policies before selling a part. About the ASE P2 test →