ASE A8 Engine Performance Practice Test

36. Technician A says the PCM advances the engine's ignition timing when it receives a voltage signal from the knock sensor. Technician B says this sensor sends an AC signal to the PCM when it detects ping or detonation. Who is correct?

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

36.

Answer A is wrong. The PCM retards the engine's ignition timing when it receives a voltage signal from the knock sensor. Retarding the engine's ignition timing helps prevent detonation (knock).

Answer B is correct. The knock sensor creates and sends an AC voltage signal to the PCM whenever it senses vibration from engine knock or ping.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

A compared catalyst monitor waveform.

37. Bank 1 Sensor 1 is the pre-catalytic converter heated oxygen sensor and Bank 1 Sensor 2 is the post-catalytic converter oxygen sensor. The waveforms above are compared to diagnose catalytic converter efficiency. Technician A says Bank 1 Sensor 2 is faulty because the two waveforms should have similar voltage peaks and fluctuations. Technician B says Bank 1 Sensor 2 is the catalyst monitor. It monitors the catalytic converter’s ability to reduce pollutants in the exhaust stream. Who is correct?

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

37.

Answer A is wrong. Bank 1 Sensor 2 is monitoring the catalytic converter’s ability to reduce pollutants in the exhaust stream. It should have much less amplitude than Bank 1 Sensor 1.

Answer B is correct. The catalytic converter uses the oxygen in the exhaust and from secondary AIR injection to breakdown harmful pollutants.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

38. An engine with variable valve timing has a rough idle, but runs smoothly at higher engine speeds. Technician A says to check the variable valve timing solenoid and its associated circuit. Technician B says this problem can be caused by unchanged contaminated oil. Who is correct?

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

38.

Answer A is wrong. Both Technicians are correct.

Answer B is wrong. Unchanged oil is a big problem. These solenoids become clogged. If the actuator is not engaging or releasing it may be stuck. Passages get clogged from unchanged and contaminated oil and gel.

Answer C is correct. Both Technicians are correct.

Answer D is wrong. Both Technicians are correct. Tap or click the Read more… button for more information.

39. Technician A says an AF (Air/Fuel) sensor is designed to reach and keep an engine at stoichiometry. Technician B says stoichiometry is 15.7:1 air to fuel mixture. Who is correct?

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

39.

Answer A is correct. An Air/Fuel sensor is designed to reach and keep a vehicle at stoichiometry.

Answer B is wrong. Stoichiometry is a (14.7:1) air to fuel mixture. This is an important ratio to remember.

Answer C is wrong. Technician A is correct.

Answer D is wrong. Technician A is correct.

40. An engine suffers from a lack of power during acceleration. A vacuum test is being performed. At 2500 RPM, the needle on the vacuum gauge drops slowly to 10 "hg. Which of these could be the cause?

  • A. A clogged catalytic converter.
  • B. Late valve timing.
  • C. A faulty head gasket.
  • D. Burned exhaust valve.

40.

Answer A is correct. If the needle drops steady during acceleration, there's a restriction in the exhaust. These test results are most likely caused by a restricted exhaust; a clogged catalytic converter.

Answer B is wrong. Late ignition timing causes a low vacuum reading between 10 "hg and 15 "hg.

Answer C is wrong. A blown head gasket allows coolant to enter the combustion chamber and causes the engine to overheat. It also results in white/gray exhaust at the tailpipe.

Answer D is wrong. A bad exhaust valve causes the needle on the vacuum gauge to fluctuate.