ASE A8 Engine Performance Practice Test

36. Which of the following creates and sends an AC voltage signal to the ECM when it detects detonation?

  • A. The throttle position sensor.
  • B. The knock sensor.
  • C. The manifold absolute pressure sensor.
  • D. The oxygen sensor.

36.

Answer A is wrong. The knock sensor creates and sends an AC voltage signal to the ECM when it senses the engine knock and pre-ignition.

Answer B is correct. The ECM 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 C is wrong. Answer B is correct.

Answer D is wrong. Answer 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 heated oxygen sensor. Technician A says to replace the Bank 1 Sensor 2 because the two waveforms should have similar voltage peaks and fluctuations. Technician B says Bank 1 Sensor 2 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. Therefore, 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 secondary AIR injection to break down 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 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. Be sure to use the correct oil; the oil's viscosity will affect the operation of a VVT system.

Answer B is wrong. Passages get clogged from unchanged oil. If the actuator is not engaging or releasing, it may be stuck. Be sure to use the correct oil; oil viscosity will affect the operation of a VVT system.

Answer C is correct. Both Technicians are correct.

Answer D is wrong. Tap or click the Read more… button for more information.

39. Technician A says an (AF) air-fuel ratio sensor senses a broader range of air-fuel mixtures than a standard oxygen sensor. 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 ratio sensor senses a wider range of air-fuel ratios (~10:1 to 20:1) than a conventional oxygen sensor.

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. A vehicle has poor acceleration. A vacuum gauge is connected to the engine's intake manifold. While steadily increasing the engine speed to 2500 RPM, the needle on the 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 steadily during acceleration, there is a restriction in the exhaust, most likely 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.