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. An engine has poor performance. A vacuum gauge is connected to an intake manifold port. 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 by 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 emits 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 has a fault 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 this 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. The manufacturer calibrates the gas cap to maintain a certain pressure in the fuel tank. Therefore, a crack in the cap will cause a leak and alter system pressure.

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

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.