ASE A1 Engine Repair Practice Test
61. A vehicle emits white-colored exhaust 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 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.
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 (piston slap).
Answer D is wrong. A loose timing belt slaps 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 center electrode's design and the ceramic insulator's length surrounding it. A spark plug with too high 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 exhaust from the turbine.