ASE A8 Engine Performance Practice Test
1. An engine with a vacuum operated EGR system has fault code P0401, poor performance, and ping and detonation. A vacuum of 18"hg is applied to the EGR valve, the engine stumbles, and there is a significant drop in RPM. Which of the following is causing this condition? The engine has:
- A. A faulty EGR position sensor.
- B. A faulty EGR valve.
- C. A clogged EGR passage.
- D. A faulty EGR vacuum solenoid.
Answer A is wrong. The EGR position sensor informs the PCM of the EGR position. The vacuum solenoid is bypassed when a vacuum pump is used to activate the EGR valve.
Answer B is wrong. When a manual vacuum pump is used to activate the EGR valve, the solenoid, its circuit, and the ECM is bypassed. The notable drop in RPM eliminates the EGR valve as the problem.
Answer C is wrong. Make sure the intake passages are open and not restricted before replacing an exhaust gas recirculation valve. When clogged with carbon, use a small wire brush to clean out the passage. The vacuum test eliminates the intake passages as the problem.
Answer D is correct. The solenoid is bypassed when a vacuum pump is used to activate the EGR valve. If the engine started stumbling, the valve opened; test the solenoid with a multimeter. This valve prevents the engine's cylinders from reaching damaging temperatures and protects the environment from NOx.
2. A cylinder power balance test indicates two adjacent cylinders are underperforming. All of the following would cause this result EXCEPT:
- A. Crossed ignition wires.
- B. A leaking head gasket.
- C. A faulty COP ignition coil.
- D. A cracked cylinder head.
Answer A is wrong. Clips keep the ignition wiring separated and help prevent leaking insulation and crossfire.
Answer B is wrong. A faulty head gasket leaking between two adjacent cylinders will affect both cylinders.
Answer C is correct. A (COP) coil on plug ignition system has a coil mounted directly over the spark plug of each cylinder. A faulty coil results in a misfire at that particular cylinder.
Answer D is wrong. A cracked cylinder head or block will cause a leak between cylinders.
3. An engine with a (COP) coil on plug ignition system cranks but will not start. A voltage meter measures 0.00 volts at each of the coil's (B+) power feeds. Which of the following is MOST likely causing this no start condition?
- A. n open in the primary circuit.
- B. The ECM's driver is faulty.
- C. Resistance in the secondary circuit.
- D. A faulty Engine Control Module.
Answer A is wrong. An open in the primary circuit will affect only one ignition coil.
Answer B is wrong. A faulty ECM Engine Control Module driver will cause no spark at only one of the coils.
Answer C is wrong. Resistance in the secondary circuit will affect only one of the coils. With (COP) or coil on plug ignition systems, a coil is placed over each spark plug eliminating the need for spark plug wires.
Answer D is correct. A loss of power from a defective ECM relay or fuse or a faulty ECM will result in no power to any of the coils and a no spark condition. This problem will also affect the fuel injectors. An (EI) electronic ignition system uses a (CKP) crankshaft position sensor. A faulty CKP sensor will also result in a no spark condition.
4. Technician A says a faulty Heated-Wire (MAF) Mass Air Flow sensor affects fuel trim resulting in a loss of power and hesitation. Technician B says the MAF sensor's tip can become contaminated with deposits affecting its signal to the engine control module. Who is correct?
- A. Technician A
- B. Technician B
- C. Both A and B
- D. Neither A or B
Answer A is wrong. A dirty or faulty (MAF) Mass Air Flow sensor affects fuel trim resulting in a loss of power, hesitation, and reduced fuel mileage.
Answer B is wrong. The (MAF) Mass Air Flow Sensor senses air flow volume in the air tube. It provides the ECM and TCM with valuable information regarding engine load.
Answer C is correct. Both technicians are correct.
Answer D is wrong. Because the heated filament gets dirty from time and wear, a filament cleaning may return the MAF's function.
5. The engine in the diagram above:
- A. Has an HEI distributor.
- B. Has a waste spark ignition system.
- C. Has sequential fuel injection.
- D. Has multiport fuel injection.
Answer A is wrong. The engine has sequential fuel injection; each cylinder gets an injector offering more control and precise timing.
Answer B is wrong. The engine has (COP) coil on plug ignition; each cylinder has an ignition coil.
Answer C is correct. Sequential fuel injection systems fire each injector individually.
Answer D is wrong. This system is different from a multiport injection system, where the PCM fires more than one injector simultaneously.