ASE A8 Engine Performance Quiz

1. An EFI engine is running rough and stalling at idle. The MAP sensor's vacuum hose is loose and cracking. Technician A says this sensor measures air mass to establish the base pulse of the engine's fuel injectors. Technician B says this sensor measures changes in intake manifold pressure. Replacing this hose will restore its path to manifold pressure. Who is correct?
2. A vehicle has a momentary hesitation only during acceleration. The MOST likely cause of this condition is:
3. A four cylinder EFI engine has an engine code indicating insufficient EGR flow. The EGR solenoid has been tested and found to be faulty. This faulty solenoid will result in which of these conditions.
4. A vehicle with an enhanced EVAP system is scanned and a code indicating a small evaporative emissions leak is detected. A loose or cracked gas cap is suspected. Technician A says the cap contains a vacuum and pressure relief valve, a small crack in the cap will not illuminate the check engine light. Technician B says the tank contains a sensor. The PCM will sense low tank pressure, set a code and illuminate the check engine light. Who is correct?
5. 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?
6. Two technicians are discussing turbochargers. Technician A says the boost pressure sensor provides the intake manifold's boost pressure to the PCM. Technician B says a leaking wastegate diaphragm affects exhaust flow through the turbine wheel. Who is correct?

7. A PCM uses all of these inputs to calculate air fuel ratio and speed control EXCEPT:
8. An engine with a viscous fan clutch is running hot only at stop lights. Technician A says this type of fan should be checked for leakage. Technician B says a defective relay may cause this fan to become inoperative. Who is correct?
9. A fuel pressure test at the fuel rail of a sequential fuel injected engine indicates low fuel pressure. All of these would cause this test result EXCEPT:
10. An oxygen sensor is sending a consistent signal of .20 volts. Technician A says this indicates a rich fuel mixture. Technician B says the PCM will adjust fuel trim to compensate for a disconnected vacuum hose. Who is correct?
11. Which of the following is LEAST likely to cause a rich fuel condition:
12. Technician A says the heater circuit in an oxygen sensor brings the sensor to operating temperature. Technician B says the engine control module uses the oxygen sensor's voltage signal to adjust the air fuel ratio in closed loop. Who is correct?
13. Two technicians are discussing a turbocharged engine. Technician A says the wastegate is a component used to control boost pressure. Technician B says when opened, the wastegate diverts exhaust gas from the turbine wheel. Who is correct?
14. An emissions test is performed on a six cylinder engine. The test indicates high levels of NOx. The MOST likely cause of this condition is:
15. Two technicians are discussing a voltage drop test. Technician A says to perform a voltage drop test if a corroded ground connection is suspected. Technician B says to perform a voltage drop test if excessive resistance is suspected. Who is correct?
16. Technician A says a stuck open PCV valve will cause a rich fuel condition. Technician B says the PCV system removes blowby gases from the crankcase. Who is correct?
17. A crankshaft position sensor's companion sprocket has a broken tooth. Technician A says the camshaft position sensor monitors crankshaft speed and rotation. Technician B says the vehicle's engine will operate and perform normally. Who is correct?
18. A vehicle has a check engine light with codes indicating a problem with the enhanced evaporative emission system and a rich fuel condition. Technician A says a defective evaporative purge valve will cause a rich air fuel ratio. Technician B says the tank pressure sensor will notify the PCM of excessive tank pressure. Who is correct?
19. A cylinder power balance test is being performed on a four cylinder engine. A spark plug wire is removed from its corresponding spark plug and a slight drop in rpm is noticed. Which of the following is correct?
Cylinder Compression Test

20. A cylinder compression test is performed on an eight cylinder engine. The test results above indicate:

Please select an answer