ASE A8 Engine Performance Practice Test

31. An EGR valve vacuum solenoid has 18 "hg. as its vacuum source. The resistance checks out OK. Vacuum pressure is manually applied to the EGR valve with a pump and a slight stumble is noticed. There is little drop in rpm. This is caused by:

  • A. A faulty vacuum solenoid.
  • B. A poor vacuum source.
  • C. A restriction in the EGR passage.
  • D. A faulty EGR position sensor.

31.

Answer A is wrong. When a manual vacuum pump is used to activate the EGR valve, the solenoid is bypassed.

Answer B is wrong. A vacuum source of 18 "hg. is enough to open the valve.

Answer C is correct. Make sure the passages are open and not clogged before replacing an exhaust gas recirculation valve. If it's clogged with carbon, use a small wire brush to clean out the passage.

Answer D is wrong. The EGR position sensor is used to inform the PCM of EGR position. It's mounted on the top and would not clog the passage.

32. A cylinder power balance test is being performed on a vehicle with sequential port fuel injection. Two adjacent cylinders are under performing. Technician A says this could be caused by a restriction in the fuel injectors. Technician B says this could be caused by leaking secondary insulation. Who is correct?

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

32.

Answer A is wrong. Both technicians are correct.

Answer B is wrong. Both technicians are correct.

Answer C is correct. Both restricted fuel injectors and leaking secondary wires will reduce the cylinder's contribution. It's important to keep the wiring separated and in the proper clips to prevent leaking insulation and cross fire. A faulty head gasket leaking between two adjacent cylinders will result in this same condition.

Answer D is wrong. Both technicians are correct.

33. A COP ignition system has no spark at any of the coils. Which of these is MOST likely causing this loss of spark?

  • A. A faulty PCM driver.
  • B. Excess resistance in the primary circuit.
  • C. Excess resistance in the secondary circuit.
  • D. No power to PCM BAT+.

33.

Answer A is wrong. A faulty PCM driver will cause no spark at only one coil.

Answer B is wrong. Resistance in the primary circuit will cause no spark at only one of the coils. This is because with COP or coil over plug ignition systems, each cylinder gets its own coil.

Answer C is wrong. Resistance in the secondary circuit will cause no spark at only one of the coils.

Answer D is correct. No power to or a faulty PCM will result in no power to any of the coils and a no spark condition. An (EI) electronic ignition system uses a (CKP) crankshaft position sensor, a faulty CKP sensor will also result in no spark at any the cylinders.

34. Technician A says the MAP sensor is located on the intake manifold and informs the PCM of intake manifold pressure. Technician B says the MAF sensor senses air flow in the air tube. It's signal indicates engine load to the PCM. Who is correct?

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

34.

Answer A is wrong. A (MAP) Manifold Absolute Pressure Sensor senses air pressure in the intake manifold.

Answer B is wrong. The (MAF) Mass Air Flow Sensor senses air flow volume in the air tube indicating engine load. These are two different sensors used by the engine's PCM.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

Diagram of automotive PCM engine control system.

35. The vehicle's engine in the schematic diagram above:

  • A. Has sequential fuel injection.
  • B. Is a wastespark ignition system.
  • C. Is on a low speed Controller Area Network.
  • D. Has multiport fuel injection.

35.

Answer A is correct. Excessive hydraulic lifter preloads will cause low manifold vacuum.

Answer B is wrong. Insufficient lifter preloads will cause valve train noise.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.