ASE Practice Test (A8: Engine Performance)
The EGR (Exhaust Gas Recirculation) valve may be closed, according to a technician. A closed EGR valve would be indicated by which of the following?
Correct answer: Spark knock
Spark knock is a symptom of an EGR valve that is always closed. The other choices are wrong because they are symptoms of an EGR valve that is always open.
What is the LEAST likely reason of a gasoline tank leak:
Correct answer: defective tank straps.
Road damage often causes fuel tank damage. Defective seams can be a cause of fuel leaks. Corrosion, after it is through the tank, will cause a fuel leak.
Blue smoke comes from the exhaust pipe of a vehicle. Technician X says that blocked cylinder head oil return passages could be the cause. Technician Y says that a stuck-open engine thermostat could be the cause. Who is right?
Correct answer: X only
Technician X is right. The blocked cylinder head oil return passages could be the cause of the blue smoke that comes from the exhaust.
What should you do first when diagnosing an engine performance problem?
Correct answer: Discuss the concern with the owner of the vehicle
All of these answers are acceptable ways to diagnosis engine performance issues. However, you need to start by talking to the customer to see what they are experiencing. Then, you can take that information and perform further diagnosis.
The plastic sensors on an electronically controlled EGR valve have melted. Technician X says excessive back pressure caused by a partially clogged exhaust system could be the cause. Technician Y says to always check for a restricted exhaust whenever replacing a failed EGR valve sensor. Who is right?
Correct answer: Both X and Y
Both technicians are correct.
All of these reduce the life of the turbocharger, except:
Correct answer: exhaust system damage.
Improper cooling affects the life of the bearings. Not changing the oil frequently causes sludge buildup. A dirty air cleaner will contaminate the air intake with dust and dirt, which shorten the life of the turbocharger.
A vehicle is being diagnosed for poor fuel economy. Engine tests show a rich exhaust gas mixture. Technician X says that a failed oxygen (O2 ) sensor could be the cause. Technician Y says that a failed engine coolant temperature sensor could be the cause. Who is right?
Correct answer: Both X and Y
Both technicians are right.
Technician X believes that paper service manuals still get used today. Technician Y believes that you should always follow recommended service procedures found in online service information. Who is correct?
Correct answer: Technician Y
Tech X is incorrect because most paper manuals are now obsolete. Today’s OEM information is all available online. That’s why you must access the procedures in the online service information for the recommended repair.
A disconnected spark plug is interpreted by the vehicle's OBD II (On Board Diagnostic Level 2) system as a misfire that could harm the three-way catalyst. On which trip will the Malfunction Indicator Lamp (MIL) be most likely turned on by the ECM or PCM?
Correct answer: 1st trip
It is most likely that on the first trip a misfire condition can occur that can damage the three way catalyst (TWC) due to overheating. Specific on board diagnostic items will cause the ECM to light up or blink the MIL, and store DTC and Freeze Frame data, even in the 1st trip; e.g., Misfire (Possible three way catalyst damage) - DTC: P0300 -P0306 is being detected.
The following below are true about the cylinder leakage test. Except:
Correct answer: a gauge reading of 100 percent indicates no cylinder leakage.
A reading of 100 percent indicates a major, total cylinder leak, either due to an incorrect crank position (valve open) or internal damage. A reading of up to 20 percent is considered normal.
An engine's intake manifold is connected to a vacuum gauge. The pointer on the gauge fluctuates rapidly between 10 and 22 in.Hg when the engine is running at 2,000 rpm. The cause could be:
Correct answer: a broken valve spring
The cause of the situation could be a broken valve spring.
What data do you need to know when looking for vehicle information for a given customer?
Correct answer: Make, model and year
To access data services, you will need the make, model and year of the vehicle in question. The model year and vehicle build date won’t provide you with enough information. Furthermore, you won’t need to get the VIN for this data.
Technician X says the on-board self-diagnostics test mode procedures should be conducted on a cold engine. Technician Y says many diagnostic trouble codes (DTC) will monitor items only when the engine control system is in closed loop. Who is right?
Correct answer: Y only
Technician Y is correct because many diagnostic trouble codes (DTC) will monitor items only when the engine control system is in closed loop. Closed loop operation requires the engine to reach a certain operating temperature before it can be entered. Technician X is wrong because the on-board self-diagnostics test mode procedures should be conducted on a warm engine (NOT a COLD engine as stated in the question) that is in closed loop because many DTCs only monitor in closed loop.
Exhaust manifold testing entails all of the following. Except:
Correct answer: checking for restricted exhaust manifold.
Most engines will require spark delivery to occur several degrees before the piston reaches top dead center.
On a vehicle that won't start, the technician discovers no spark and no injector pulses. It's possible that the cause is a failure:
Correct answer: crankshaft position (CKP) sensor
The cause of the problem could be a failed of a crankshaft position (CKP) sensor.
When using a diagnostic strategy to investigate a drivability issue, which of these actions should come last in the process?
Correct answer: Verify repair
After you’ve done the repair, you need to make sure it was complete. This is the final step in the process. All of the other procedures should be done prior to this.
What component does the PCM or ECM monitor to assess the catalytic converter's status and, if it fails, set a DTC (Diagnostic Trouble Code)?
Correct answer: Front and rear O2 (oxygen) sensors
On vehicles equipped with OBD II, use of two oxygen sensors is required to monitor catalytic converter efficiency. The front oxygen sensor is located before the catalytic converter (upstream) and the rear oxygen sensor is located after the converter (downstream). During closed loop fuel control, the ECM compares the signals from the two oxygen sensors. One important point to remember is that a rear O2 sensor is used only for diagnostics. It usually has no influence on engine operation or driveability.
Replacement of an ignition module entails all of the following. Except:
Correct answer: dielectric silicone is used to seal the mating surface.
Sealing of mating surfaces has nothing to do with module replacement.
At idle, a return-type electronic fuel injection (EFI) system produces a lot of fuel pressure. Which of these possibly be the source of the problem?
Correct answer: Low manifold vacuum
The cause of the problem could be low manifold vacuum.
Which of the following is an unapproved method of obtaining DTC?
Correct answer: Cycling the malfunction indicator lamp on and off
It isn’t approved to cycle the malfunction indicator lamp on and off. On vehicles with adjustable timing, specifications and setup procedures are on the underhood label. The other three answers are appropriate methods.
A NO START condition is being diagnosed on a vehicle with electronic fuel injection (EFI) and distributorless ignition. Technician X says you should only use a DMM (Digital Multimeter) to check voltage values on PCM (Powertrain Control Module). Technician Y says you should use a tool to check for spark at one of the spark plugs. Who is right?
Correct answer: Both X and Y
Both technicians are correct.
Which of the following could lead to a catalytic converter overheating?
Correct answer: A disconnected spark plug wire
A disconnected spark plug wire could be the cause a catalytic converter to overheat.
Technician X believes that when the ignition coil is failing, the engine might misfire under load. Technician Y believes the pickup coil must have dielectric grease under it. Who is correct?
Correct answer: Both Technicians
Both techs are correct. When the ignition coil is failing it might cause the engine to misfire. Tech Y is also right that the pickup coil must contain dielectric grease under it.
On an electronic distributor ignition (DI) system, a 12 volt test light is attached from the negative primary coil terminal to ground. While cranking the engine, the light flutters. When a spark tester is attached from the coil secondary wire to ground while revving the engine, it does not light. Which of the following is the MOST LIKELY reason for the problem?
Correct answer: Defective ignition coil
The test light going off and on indicates that the ignition coil triggering device is working but the failure of a spark indicates a coil failure.
Any of these factors could result in engine detonation (knock). Except:
Correct answer: retarded ignition timing.
A retarded ignition timing could not be a cause of engine detonation.
After a vehicle's battery has been discharged or disconnected, which of the following could cause it to run poorly?
Correct answer: Learned value has been lost from RAM
If battery power is lost the learned value from the RAM may be lost. RAM data is electronically retained which means that it is always to some extent volatile; that is, data storage could be described as temporary - if the circuit is opened, RAM data is lost. It should be noted that most PCMs use only fully volatile RAM. In other words, when the ignition circuit is opened all RAM data is dumped. A second type of RAM is used in some PCMs. This is non-volatile RAM (NV-RAM) (or KAM-Keep alive memory) in which data is retained until either the battery is disconnected or the PCM is reset, usually by depressing a computer reset button, which temporarily opens the circuit. Codes and failure strategy (action sequence) would be written to NV-RAM and retained until reset.
Two technicians are discussing emission diagnosis. Technician X says an ignition misfire will increase CO and HC emissions and set a DTC (Diagnostic Trouble Code). Technician Y says a misfire caused by a lean condition will increase HC and CO emissions without a DTC set. Who is right?
Correct answer: X only
Technician X is correct because all misfires set a Specific DTC and will increase HC and CO. Technician Y is wrong because a lean misfire also sets a DTC and will not increase HC and CO.
While the engine is running, a technician pulls the PCV valve out of the valve cover and plugs the valve opening. There are no changes in engine operation. Technician X says that the PCV valve could be stuck in the open position. Technician Y says that the hose between the intake manifold and the PCV valve could be plugged. Who is right?
Correct answer: Y only
Technician Y is right. The hose between the intake manifold and the PCV valve could be plugged.
The balance of fuel injector is checked using a scan tool. What should the expected result be if the injector is working properly when following standard procedure?
Correct answer: Engine RPM should decrease with each injector that’s turned off
Engine RPM will decrease every time an injector is turned off. The exception is when there’s a fault in the cylinder. There should be no change in ECT voltage.
A technician discovers one injector has failed but is receiving good power supply during an injector power balancing test. What should the next step be?
Correct answer: Continuity check between PCM and injector
The recommendation by most ESM is to do a continuity check between the PCM and injectors, when adequate power is available to the injector.