A8 Engine Performance

A-8 Engine Performance


1. An EGR valve vacuum solenoid has 18 Hg. as its vacuum source. The resistance checks out OK. Vacuum pressure is manually applied to the valve with a pump and a slight stumble is noticed. There is little drop in RPM. The most-likely cause of this is:

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

3. A COP ignition system has no spark coming from any of the coils. Which of these is most likely the cause?

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

5. Technician A says a throttle position sensor is considered a potentiometer. Technician B says this sensor can be tested with an ohmmeter. Who is correct?

6. After performing a wet cylinder compression test, all of the cylinders remain low. Technician A says this may be incorrect camshaft timing. Technician B says this may be worn piston rings. Who is correct?

7. A vacuum gauge is connected to the intake manifold of an engine. The needle fluctuates between (15 and 20 in Hg) at idle. This reading indicates:

8. Technician A says a stuck closed EGR (exhaust gas recirculating) valve will cause an engine to stumble or stall. Technician B says a stuck open EGR valve will cause detonation. Who is correct?

9. At idle, a vehicle is emitting black smoke from its tailpipe. The most likely cause of this condition is:

10. A vehicle has a lack of power while accelerating. A vacuum gauge reads 10Hg at 2500 RPM. The most-likely cause of this reading is:

11. Which of these is least-likely to cause a rich fuel condition:

12. Technician A says a 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 fuel trim 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 emission 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 lean fuel condition. Technician B says the PCV system removes blowby gases from the crankcase. Who is correct?

17. Technician A says the crankshaft position sensor monitors crankshafts speed and rotation. Technician B says a permanent magnet crankshaft position sensor always has three wires. Who is correct?

18. Technician A says a defective evaporative purge valve may cause a rich air fuel ratio. Technician B says an evaporative pressure sensor is used to notify the PCM of gas 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.

20. A cylinder compression test is performed on an eight cylinder engine. These results most likely indicate:

21. Technician A says the PCM will advance ignition timing when it receives a voltage signal from the knock sensor. Technician B says this sensor sends an AC signal to the PCM when it detects ping or spark knock. Who is correct?

22. There's a misfire at the #3 cylinder of a COP ignition system. There is no power at the Bat+ terminal of the coil. Which of these is most-likely the cause?

23. An enhanced EVAP system has a code indicating a gross leak detected. Which of the following is most likely the cause?

24. A catalytic converter is damaged from heat. Technician A says this damage is most likely caused by cylinder misfiring. Technician B says this is most likely caused by low fuel volume. Who is correct?

25. A vehicle has a fuel trim of +5 at idle and +25 at cruise. The vehicle has a steady oxygen sensor reading of 800Mv. When the vacuum hose is disconnected from the brake booster check valve there is no change in the oxygen sensors reading. The most likely cause for this reading is:

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