ASE A8 Engine Performance Practice Test

31. After performing a wet compression test, the pressure in each cylinder has increased but remains below specifications. Technician A says the engine has incorrect valve timing. Technician B says worn piston rings have caused these results. Who is correct?

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

31.

Answer A is wrong. Incorrect valve timing results in low compression readings in all of the engine's cylinders.

Answer B is correct. If the engine has worn piston rings, the pressure readings increase after injecting oil.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

32. A vacuum gauge is connected to a port on the intake manifold of an engine with poor performance. The needle on the gauge fluctuates between 15 "hg and 20 "hg vacuum at idle. This vacuum gauge reading indicates:

  • A. A normal condition.
  • B. Late ignition or valve timing.
  • C. A burned exhaust valve.
  • D. A restricted exhaust.

32.

Answer A is wrong. A gauge that reads steady (17 "hg - 21 "hg) indicates a normal running engine. Vacuum is measured inches of mercury vacuum or "hg.

Answer B is wrong. A gauge that reads a steady low (15 "hg - 20 "hg) indicates late valve or ignition timing, leaking manifold gasket, low compression, leaking carburetor or a stuck throttle valve.

Answer C is correct. A gauge that fluctuates between (15 "hg and 20 "hg) indicates a stuck valve or an engine misfire.

Answer D is wrong. A gauge needle that drops slowly at idle indicates a clogged or blocked exhaust.

33. Technician A says a stuck closed (EGR) exhaust gas recirculating valve causes an engine to stumble or stall. Technician B says a stuck open EGR valve results in detonation. Who is correct?

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

33.

Answer A is wrong. A stuck open, not closed EGR valve will cause an engine to stumble or stall.

Answer B is wrong. A stuck closed, not open EGR valve will cause harmful detonation.

Answer C is wrong. Neither technician is correct.

Answer D is correct. Neither technician is correct.

34. A vehicle is emitting black smoke from its tailpipe at idle. Which of these could be the cause?

  • A. A leaking fuel injector.
  • B. Worn piston rings.
  • C. A blown head gasket.
  • D. Leaking valve seals.

34.

Answer A is correct. A leaking fuel injector causes a rich air-fuel mixture. A rich fuel condition causes black-sooty exhaust. (Fuel)

Answer B is wrong. Worn rings cause blue-gray colored exhaust. (Oil)

Answer C is wrong. A blown head gasket causes white-gray exhaust. (Coolant)

Answer D is wrong. Leaking valve seals produce blue-gray exhaust. (Oil)

35. A vehicle with an enhanced EVAP system has a code indicating a small evaporative emissions leak has been detected. Technician A says a small crack in the gas cap will result in this code. Technician B says the fuel tank of an enhanced EVAP system contains a sensor that senses low tank pressure. Who is correct?

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

35.

Answer A is wrong. A crack in the cap will alter system pressure. The gas caps are calibrated by the manufacturer to maintain a certain pressure in the tank.

Answer B is wrong. Today's enhanced EVAP systems use a fuel tank pressure sensor that measures pressure at the tank. They set a code and illuminate the check engine light if the vehicle has a faulty, loose, or damaged gas cap.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.