Automotive Diagnostic Procedures and Troubleshooting, Exams of Engineering

Download Automotive Diagnostic Procedures and Troubleshooting and more Exams Engineering in PDF only on Docsity! ASE A8 Engine Performance practice test questions and answers D. The PCV valve should rattle when shaken back and forth. When the thumb is placed over the end of the PCV valve with the engine idling, the plunger should snap back. A water manometer can be used to check the crankcase for vacuum at idle. There is no blowby test that is performed on the PCV system. - answer All of the following are tests performed on the PCV system EXCEPT: A. The rattle test B. The snap- back test C. Crankcase vacuum test D. Blowby test C. Faulty secondary ignition components are common causes of ignition module failure. Some modules require the use of dielectric grease to aid in dissipating heat. A fouled spark plug would cause an engine miss, but would not cause the ignition module to fail. Loose module mounting screws will cause the module to fail prematurely. - answer Which of the following is the LEAST LIKELY cause of ignition module failure? A. An open spark plug wire B. No dielectric grease under the module C. A fouled spark plug D. Loose module mounting screws A. A partially restricted fuel return hose would cause the fuel pressure to be higher than it should. This would cause poor fuel economy without affecting drivability. A stuck open fuel regulator would lower fuel pressure, possibly causing a no-start, but would not cause a fuel economy complaint. - answer A sequential fuel- injected vehicle has poor fuel economy, yet starts and runs fine. Technician A says the fuel return line may be partially restricted. Technician B says the fuel pressure regulator may be stuck open. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician A. The EGR system is used to lower combustion chamber temperature . If the EGR system does not operate, then the engine will operate too hot, causing spark knock and elevated oxides of nitrogen (NOx) reading. An inoperative EGR system will raise combustion chamber temperatures and cause the engine to run hotter. - answer Technician A says if the passages in the exhaust gas recirculation (EGR) system get plugged up with carbon, then the engine could spark knock. Technician B says if the EGR passages get plugged up, then the engine will not run hot enough for complete combustion. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician C. Both. When the power transistor in the ignition control module opens the primary ignition circuit, the build-up magnetic field in the coil collapses. This produces the secondary voltage to jump the gap at the spark plug. The voltage that the coil produces can be broken down into three different types: "required voltage" (the voltage required to jump the gap at the spark plug), "available voltage" (the voltage available to jump the gap at the spark plug), and the "reserve voltage" (the voltage in reserve after the spark plug fires). As the engine accelerates, the required voltage goes up. If there is not enough voltage in reserve, then the engine will miss. - answer Technician A says a coil with weak reserve voltage could cause a miss under acceleration. Technician B says the ignition coil only produces enough secondary voltage to jump the spark plug gap. Who is correct? A. Tech A B. Tech B C. Both. Compression reading at idle should be approximately half of the cranking compression or typically between 60-90 psi. Compression reading at 2,000 rpm should typically be between 30-60 psi. As with cranking compression, the running compression of all cylinders should be equal. - answer A technician is performing a running compression test on a vehicle with suspected worn ring and cylinder problems. Technician A says running compression should be half of static compression at idle. Technician B says during a running compression test, the technician should increase the engine speed to 2,000 rpm, and the running compression should be lower than at idle. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician C. The resistance value of the primary circuit in the coil is crucial for good secondary circuit operation. A resistance measurement of the primary to secondary measures the secondary winding resistance and is an important test. The secondary ignition system is a high-voltage, low-amperage circuit, While the secondary voltage readings are important, the amperage is not measured. The primary amperage is very important. If the primary amperage was too low, then the secondary voltage would be low. - answer Which of the following is LEAST LIKELY to be a test that would be performed on an ignition coil? A. Resistance primary to primary B. Resistance primary to secondary C. Secondary circuit amperage D. Primary circuit amperage B. A reading of 5 psi back pressure at 2,000 rpm is excessive and would indicate an exhaust restriction. Exhaust back pressure should not exceed 2.5 psi at 2,500 rpm. The catalytic converter can come apart causing an exhaust restriction. Sometimes this can be found by performing a converter rattle test. - answer A vehicle with low engine power is being diagnosed. Technician A says an exhaust back-pressure test should be at least 5 psi at 2,000 rpm. Technician B says the catalytic converter may have come apart and be restricting exhaust flow. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician D. Neither. The EONV system does not use a pump; instead, it closes the vent valve and monitors the fuel tank pressure as the fuel cools off. If the EVAP system is not leaking, then a specific amount of vaccum will be present on cool down. The vent valve is a naturally open valve that is closed by the PCM (powertrain control module) when it runs an EVAP monitor. Some systems use a leak detection pump to monitor the EVAP for leaks, but the EONV system uses the natural physics of heat and pressure. - answer Technician A says the filter on the engine-off natural vacuum pump (EONV) should be serviced with the regular oil change interval. Technician B says the EONV EVAP system does not use a vent valve. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician A. OBD II requires the use of a standardized 16-pin DLC, not 26-pin. OBD II requires the use of a standardized list of DTCs. OBD II vehicles can perform rationality tests on components. OBD II requires the use of a standardized communication protocol. - answer All of the following apply to OBD II vehicles EXCEPT: A. A standardized 26-pin data link connector (DLC) B. A standardized list of diagnostic trouble codes (DTCs) C. The ability to perform rationality tests on components D. A standardized communication protocol D. Neither. If the test light flickers on and off while cranking, then the ignition module is doing what it is supposed to do. If the test light flickers on and off while cranking, then the pickup coil is doing what it is supposed to do. When diagnosing a no-start with no spark, a test light should be placed between the negative terminal of the ignition coil and ground. Crank the engine and watch the test light. If the ignition control module and it's trigger device are working correctly, then the test light will flicker on and off. - answer A test light is connected between the negative side of the ignition coil and ground and the engine is cranked. Technician A says a flickering test light could be caused by a defective ignition module. Technician B says a flickering test light could be caused by a defective pickup coil. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician D. If the TPS gets a bad spot on it, then the vehicle will hesitate. If the purge control solenoid allows the canister to purge at idle, then a hesitation can occur on acceleration and tip-in. A defective EGR valve can open too soon, causing an acceleration tip-in complaint. A defective secondary air pump motor would cause excessive emissions but would not cause a tip-in complaint. - answer A multi-port fuel injection vehicle has a tip-in hesitation when warm. All of these could be the cause EXCEPT: A. Throttle position sensor (TPS) B. Canister purge control solenoid C. EGR C. Both. Any time a voltage drop test is being performed, the circuit being tested must be powered up and operating. Any resistance in the circuit will show up as a voltage drop. - answer When testing for voltage drop in the power and ground distribution circuits, Technician A says the circuit being tested must be operating. Technician B says any corrosion adds unwanted resistance. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician C. Both. A defective alternator and high resistance in the field circuit could cause low output from the alternator. - answer When the alternator belt and belt tension are satisfactory and the alternator output is low, Technician A says the alternator may be defective. Technician B says the problem could be high resistance in the alternator field circuit. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician A. Any erratic ohmmeter readings when the pickup coil leads are moved indicates a partially open circuit or that it is intermittently making good connection and the pickup coil should be replaced. Pickup coils are magnetic pulse generating components and they all have a resistance value, usually between 500 to 1,500 ohms. An infinite reading on a pickup coil would indicate the need for replacement. - answer A pickup coil resistance is being tested with an ohmmeter. Technician A says when the pickup coil leads are moved, an erratic ohmmeter reading indicates the need for replacement. Technician B says that an infinite ohmmeter reading between the pickup coil terminals is normal on some pickup coils. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician B. Not all vehicles have a Schrader valve for testing the fuel pressure. Some vehicles require the installation of a test port so a pressure gauge can be connected. If high fuel pressure is found, then a restricted or plugged fuel return line could be the cause. - answer While testing fuel pressure on a multi-port fuel injection engine, Technician A says there will always be a Schrader test port for fuel system testing. Technician B says that a high fuel pressure reading could be the result of a plugged return line. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician A. If the secondary air is constantly injected upstream into the exhaust manifold, then the extra oxygen tricks the O2 sensor into sending a lean signal to the PCM, causing the PCM to command an increase in fuel. A constant lean oxygen sensor signal would be the result. This would have no effect on any spark knock. This would not cause the exhaust to overheat. - answer A stuck air-switching valve that constantly sends air pump output to the exhaust manifold will most likely result in which of the following conditions? A. Poor fuel economy B. A constant rich oxygen sensor signal C. Engine spark knock D. The exhaust to overheat C. Both. Some PCMs require the programmable read only memory (PROM) chip to be transferred from the old PCM when replacing. Some PCMs use an electronically erasable programmable read-only memory (EEPROM) chip that requires the PCM be flash programmed when replaced. - answer Technician A says some PCMs require a program chip to be transferred from the old PCM to the new PCM when replacing. Technician B says some PCMs require flash programming when replacing. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician B. A defective bearing would make noise all the time, not just at start up or acceleration. If the tensioner fails to keep the belt tight, then the belt could squeal on start up or acceleration. - answer A vehicle emits a belt squeal when starting and on acceleration. Technician A says the alternator bearings may be defective. Technician B says the alternator belt automatic tensioner may be defective. Who is correct? A. Tech A B. Tech B C. Both Technicians D. Neither technician B. Propane can be used to locate a vacuum leak, but it is not the preferred method. The best way and preferred method to locate a vacuum leak is with a smoke machine. Water can damage components and allow the formation of corrosion. Throttle body cleaner can be a fire hazard around a running engine. - answer When a vacuum leak is suspected for a high idle complaint, the preferred testing method would be: A. Propane B. Smoke C. Water D. Throttle body cleaner A. The PCM controls the canister purge solenoid and allows canister purging based on inputs from other sensors like ECT, TPS, and heated O2. A. Tech A B. Tech B C. Both technicians D. Neither technician C. Both. Aeration is the formation of air bubbles. Overfilling the crankcase with oil can cause this aeration, and the air bubbles can lead to lifter noise. Another cause of lifter noise is the use of engine oil that is too thin or the viscosity too low. - answer Technician A says that an overfilled crankcase can cause hydraulic lifter noise due to oil aeration. Technician B says using motor oil with a viscosity rating that is too low can cause hydraulic lifter noise. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician C. Both. A good oxygen sensor should rapidly switch from 100 to 900 millivolts. This can be tested with a DMM set on the 2-volt scale or with an oscilloscope. - answer Technician A says that a DMM can be used to check an oxygen sensor. Technician B says that to check an oxygen sensor, you can use an oscilloscope. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician D. Scan tool data is valuable information when testing the engine coolant temperature sensor circuit. Resistance value is valuable information when testing the engine coolant temperature sensor circuit. Voltage value is valuable information when testing the engine coolant temperature sensor circuit. The amperage vale is not used when testing the engine coolant temperature sensor circuit. - answer When testing the engine coolant temperature sensor circuit, all of the following are used EXCEPT: A. Scan tool data B. Resistance value C. Voltage value D. Amperage value A. The fan is used to circulate air through the radiator at a stop or when idling and temperatures are high. A defective fan could cause the overheating complaint. If the thermostat was opening too soon, then the vehicle would take a long time to reach operating temperature, if it reached it at all. - answer A vehicle is being diagnosed for an overheating complaint while at idle. Technician A says the electric cooling fan may be defective. Technician B says that the thermostat may be opening too soon. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician A. With a negative-temperature coefficient sensor, as temperature goes up, resistance goes down. As the engine warms up, the resistance of the ECT goes down. A lower-than-specified reading would send a signal indicating a warmer-than-actual engine temperature. On a warm engine, this would have little is any effect on starting. On a cold engine, however, this could cause hard starting. - answer Resistance on a negative-temperature coefficient coolant sensor is being tested against specifications. Technician A says a resistance reading lower than specifications would send a signal indicating warmer-than-actual engine temperature. Technician B says if the resistance is lower than specifications, the engine may exhibit hard starting when warm. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician A. Late valve timing will cause the valves to open and close at the wrong time in relation to piston position. This will cause a low vacuum reading. The vacuum gauge should be connected to manifold vacuum, not venturi vacuum. - answer A vacuum gauge indicates low vacuum (12 inches of mercury). Technician A says late valve timing will cause a low vacuum reading. Technician B says to connect the gauge to a venturi vacuum port. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician D. If there is no oxygen in the exhaust, then this indicates a rich condition. The PCM will decrease fuel injector pulse width, not increase it. If there is a lean condition, then STF will show a plus sign indicating it is adding fuel. The PCM increases or decreases the fuel injector pulse width to control the air/ fuel mixture based on what the oxygen sensor signal sends. - answer Technician A says the PCM will increase the fuel injector pulse width if there is no oxygen in the exhaust. Technician B says if there is a lean condition, then the short-term fuel trim (STF) will show a minus value on the scan tool. Who is correct? A. Tech A B. Tech B C. Both technicians D. Neither technician D. If the belt tensioner fails to keep the belt at the proper tension, then the belt can become noisy. If a belt becomes glazed, then it will slip and cause noise. Belt alignment problems will cause premature belt failure as well as noise. An overtightened belt can cause premature component failure, such as water pump and alternator, but does not cause noise. - answer Which of the following is the LEAST LIKELY cause of alternator drive belt noise?