ASE A8 Engine Performance Practice Test

16. Technician A says a stuck open PCV valve will result in a rich air fuel ratio. Technician B says the PCV system removes blowby gases from the engine's crankcase. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

16.

Answer A is wrong. A stuck open PCV valve will cause a lean condition, the PCM will attempt to adjust the air fuel ratio accordingly.

Answer B is correct. The PCV system protects the crankcase from blowby bypassing the piston rings and contaminating the engine oil. Vacuum draws blowby into intake manifold for re-combustion when the (PCV) positive crankcase ventilation valve opens.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

17. An engine with an electronic ignition system will not start. There is no spark at any of the ignition coils. Technician A says the crankshaft position sensor serves as a triggering device for this ignition system. A faulty crankshaft position sensor will result in this no start condition. Technician B says the engine's crankshaft position sensor requires a triggering wheel or tone ring to function properly. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

17.

Answer A is wrong. The crankshaft position sensor monitors crankshaft speed and rotation.

Answer B is wrong. On some engines the tone ring is located on the crankshaft. It's most often located on the harmonic balancer or crankshaft sprocket though. A broken or damaged tooth on the sensor's tone ring or companion sprocket will result in an engine misfire or a no-start condition.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct. Click the read more section for more information.

18. A vehicle has a check engine light with codes indicating a problem with the enhanced evaporative emission system and a rich fuel condition. Technician A says a defective evaporative purge valve will cause a rich air fuel ratio. Technician B says the tank pressure sensor will notify the PCM of excessive tank pressure. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

18.

Answer A is wrong. The evaporative purge valve opens to allow fuel vapor to pass from the evaporative canister to the intake manifold for combustion. Both technicians are correct.

Answer B is wrong. A tank pressure sensor is used to notify the PCM of tank pressure.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

19. A cylinder power balance test is being performed on a four cylinder engine. The #1 cylinder is disabled and a slight drop in rpm is noticed. Which of the following is correct?

  • A. This is normal.
  • B. A significant drop should be indicated.
  • C. There should be no drop at all.
  • D. There is no such thing as an engine cylinder power balance test.

19.

Answer A is wrong. This is not considered normal, especially with a four cylinder engine. The engine should begin to stumble and loose its balance from the loss of the cylinder's power contribution.

Answer B is correct. A significant drop in rpm should be noticed.

Answer C is wrong. A significant drop in rpm should be noticed.

Answer D is wrong. An engine cylinder power balance test indicates the power of each cylinder, testing its effectiveness compared to the others.

Cylinder Compression Test

20. A cylinder compression test is performed on the eight cylinder engine in the illustration above. These test results indicate:

  • A. Burned exhaust valves.
  • B. Weak piston rings.
  • C. A faulty head gasket.
  • D. Incorrect valve timing.

20.

Answer A is wrong. To check for a burned exhaust valve inject some oil in the cylinder and test again. If the pressure increases it's because the oil has improved the seal between the piston rings and the cylinder. If it doesn't increase a valve is most likely the problem.

Answer B is wrong. A technician will know if it has faulty piston rings if the compression increases after injecting oil.

Answer C is correct. When there are low compression pressures in adjacent cylinders the head gasket is leaking compression between the two or there is a crack in the deck or cylinder head. It is usually the head gasket.

Answer D is wrong. Improper valve timing would not result in this condition. It would affect more cylinders.