ASE A1 Engine Repair Practice Test
61. A vehicle has white-colored exhaust emitting from its tailpipe at all engine speeds. Which of these could be the cause?
- A. Worn piston rings.
- B. A leaking head gasket.
- C. Worn valve seals.
- D. A leaking fuel injector.
Answer A is wrong. Worn piston rings result in blue/gray exhaust.
Answer B is correct. A leaking head gasket results in a coolant leak from the jacket into the cylinder producing white/gray exhaust.
Answer C is wrong. Leaking valve seals result in oil entering the combustion chamber.
Answer D is wrong. A leaking fuel injector results in black sooty exhaust.
62. RTV (Room Temperature Vulcanizing) aerobic sealant:
- A. Cures in the absence of air.
- B. Is safe for use with oxygen sensors.
- C. Is used primarily inside of the engine.
- D. Cures in the presence of air.
Answer A is wrong. RTV (Room Temperature Vulcanizing) is an aerobic sealant meaning that it cures in the presence of air.
Answer B is wrong. Keep RTV away from sensors. Don't use RTV sealant on high-temperature components like oxygen sensors and exhaust manifolds.
Answer C is wrong. Anaerobic sealers are used on smooth, machined components and dry in the absence of air.
Answer D is correct. Pliable silicone sealants like RTV are most common when repairing or rebuilding an engine. They absorb engine vibrations and fill imperfect surfaces on engine parts.
63. A high mileage engine has a knocking sound that goes away as it warms and reaches operating temperature. Which of these is MOST likely causing this noise?
- A. Loose crankshaft main bolts.
- B. Loose flywheel bolts.
- C. Piston to wall clearance.
- D. A loose timing belt.
Answer A is wrong. A loose crankshaft main bolts are not likely to go away as the engine reaches operating temperature.
Answer B is wrong. Loose flywheel bolts are not likely to go away as the engine reaches operating temperature.
Answer C is correct. The piston is rocking back and forth in its bore, it expands as the engine reaches operating temperature, the clearance between it and the cylinder wall decreases, and so does the noise known as piston slap.
Answer D is wrong. A loose timing belt makes a slapping sound at the front of the engine whenever it is running.
64. Technician A says preignition occurs when a flame front ignites in the combustion chamber before the spark plug fires. Technician B says installing the wrong spark plug in an engine can result in detonation. Who is correct?
- A. Technician A
- B. Technician B
- C. Both A and B
- D. Neither A or B
Answer A is wrong. There are several causes for these conditions. Most have to do with temperature and timing.
Answer B is wrong. The heat range of a spark plug depends on the design of the center electrode and the length of the ceramic insulator surrounding it. A spark plug with too high of a heat range can cause ping, detonation, and preignition problems.
Answer C is correct. Both technicians are correct. Detonation is caused by colliding flame fronts in an internal combustion engine.
Answer D is wrong. Preignition is when a flame ignites in the combustion chamber before the spark plug fires and reveals itself as a slight knocking sound heard during acceleration.
65. A turbocharged engine emits blue-gray exhaust. Which of these could be the cause?
- A. A leaking fuel injector.
- B. Faulty turbocharger oil seals.
- C. A leaking head gasket.
- D. A faulty turbocharger wastegate.
Answer A is wrong. Leaking fuel injectors result in black-colored (fuel) exhaust and a rich air-fuel ratio.
Answer B is correct. Turbocharger oil seals are not rubber o-rings. Instead, they are heat-resistant steel rings that resemble piston rings. Excessive crankcase pressure, shaft end-play, a clogged or restricted oil drain, and oil seal failure result in oil entering the turbine housing—the burning oil results in the blue-gray exhaust.
Answer C is wrong. A leaking head gasket results in the white-gray (coolant) exhaust.
Answer D is wrong. The wastegate opens to divert some of the exhaust away from the turbine.