Chapter 29-34 test
The mass airflow (MAF) sensor measures changes in the intake manifold pressure that result from changes in engine load and speed.
False
The throttle stop screw on modern throttle bodies is used to adjust the idle speed.
False
Tuned exhaust manifolds are primarily designed to reduce noise.
False
When intake air is compressed, its temperature decreases significantly.
False
CPI [central multiport injection] injectors are located in the lower half of the intake manifold.
True
Carbon dioxide [CO2] is a greenhouse gas and may be the major cause of global warming.
True
Exhaust manifolds for most vehicles are made of cast or nodular iron.
True
Fuel trim can be monitored for diagnostic purposes.
True
Hydrocarbon and carbon monoxide exhaust emissions are highest when the engine is cold.
True
IAC motor damage may result if throttle body cleaner is allowed to enter the motor.
True
If the IAC pintle is extended too far, the motor can be damaged during installation.
True
If the PCV valve is stuck in the open position, a lean air/fuel ratio may cause a rough idle or engine stalling.
True
In a returnless system, the pressure regulator is in the fuel tank and excess fuel is released to the tank.
True
It is impossible to visually check the spray pattern and volume of port system injectors.
True
Large amounts of CO2 in the exhaust are desirable.
True
Many mufflers are produced with drain holes drilled into them to allow condensation to drip out.
True
Most current fuel pumps are installed inside the fuel tank.
True
On modern vehicles, the fuel pump is shut off when the air bag is deployed.
True
Other than inspecting the electrical connections, there are usually no physical checks to mass airflow or manifold absolute pressure sensors.
True
Poor EGR gas flow can cause detonation (spark knock).
True
Some vehicles have two fuel pumps: an in-tank pump and a second pump mounted under the vehicle.
True
The LTFT works to bring the STFT close to a 0 percent correction.
True
The PCM may order a richer mixture when the engine is overheating.
True
The engine must be at normal operating temperature before the O2 sensor is tested.
True
The fuel strainer serves as a filter, stopping any rust or dirt that may be in the fuel from entering into the fuel pump.
True
An I/M 240 test lasts _____ minutes. Select one: a. two b. four c. six d. eight
four
Each fuel injector has a _____-wire connector. Select one: a. one b. two c. three d. four
two
In an engine in good condition running at 2,000 rpm, with a working EGR system, NOX should be below _____ ppm. Select one: a. 100 b. 200 c. 1,000 d. 1,750
100
In a turbocharger, the turbine and compressor wheels rotate at speeds up to ______. Select one: a. 10,000 rpm b. 50,000 rpm c. 100,000 rpm d. 150,000 rpm
100,000 rpm
NOX emissions are caused by nitrogen and oxygen uniting at cylinder temperatures above ______. Select one: a. 250°F (121°C) b. 500°F (260°C) c. 2,500°F (1,371°C) d. 5,000°F (2,760°C)
2,500°F (1,371°C)
A turbocharged engine is running with 10 psi (69 kPa) of turbo boost. At what pressure is air being fed into the engine when the engine is operating at sea level? Select one: a. 4.7 psi (32 kPa) b. 10 psi (69 kPa) c. 14.7 psi (101 kPa) d. 24.7 psi (170 kPa)
24.7 psi (170 kPa)
Which of the following is a typical fuel filter replacement interval? Select one: a. 30,000 miles (48,280 km) b. 100,000 miles (160,000 km) c. 50,000 miles (80,470 km) d. 15,000 miles (24,140 km)
30,000 miles (48,280 km)
An oxygen sensor must heat up to approximately _____ before functioning in its closed loop mode. Select one: a. 200°F (93°C) b. 400°F (204°C) c. 600°F (316°C) d. 800°F (427°C)
600°F (316°C)
Detonation sensors are being discussed. Technician A says most detonation sensors produce an analog signal. Technician B says the detonation sensor may be mounted in the exhaust. Who is correct?
A only
Fuel trim is being discussed. Technician A says a positive fuel-trim value means the PCM detects a lean mixture and is increasing the pulse width to add more fuel to the mixture. Technician B says LTFT [long-term fuel trim] is erased when the ignition is turned off. Who is correct?
A only
Technician A says an I/M 240 test is four minutes long. Technician B says the test cycle includes acceleration, deceleration, and cruising on an actual road test. Who is correct?
A only
Technician A says an SFI is more efficient than an MPI injection because fuel is injected only when the intake valve is open, so the fuel can't condense when the intake valve is closed. Technician B says an MPI injection system can shut down the injector for a misfiring cylinder, preventing catalytic converter overheating. Who is correct?
A only
Technician A says an air/fuel ratio sensor responds to minor changes in the air/fuel mixture. Technician B says that when an air/fuel ratio sensor is used on an OBD-II vehicle, both the upstream and downstream sensors must be air/fuel ratio type sensors. Who is correct?
A only
Technician A says diesel fuel is a light fuel oil and is denser [heavier] than gasoline. Technician B says diesel fuel is not as good a lubricant as gasoline; therefore wear on piston rings and cylinder walls is a greater problem for diesel engines. Who is correct?
A only
Technician A says if the EVAP system is purging vapors from the charcoal canister while the engine is idling, rough engine operation will occur. Technician B says the system should not have more than 0.5 liter of flow during the 240 seconds of an I/M 240 test. Who is correct?
A only
Technician A says low fuel pressure can be caused by a restricted fuel filter. Technician B says low fuel pressure can be caused by a kinked fuel return line. Who is correct?
A only
Technician A says piezoelectric injectors rely on stacked crystals that expand when a voltage is applied. Technician B says piezoelectric injectors are slower acting than solenoid-type injectors. Who is correct?
A only
Technician A says the air/fuel ratio of a GDI [gasoline direct injection] engine can be as high as 60 to 1. Technician B says because the air/fuel ratios are so lean, GDI engines require lower compression ratios to prevent detonation. Who is correct?
A only
Technician A tests for a restricted exhaust with an exhaust pressure gauge. Technician B uses a digital infrared pyrometer. Who is correct?
A only
A vehicle with a leaking nylon fuel supply line is being repaired. Technician A says replace the nylon fuel line with a section of double-wall steel fuel line, using short lengths of rubber fuel hose and screw clamps to connect to the filter and fuel tank to the steel line. Technician B says use an OEM nylon fuel line assembly. Who is correct?
B only
Short-term and long-term fuel trim readings are being discussed. Technician A says a scale of 0 to 255 is used. Technician B says percentage is used. Who is correct?
B only
Technician A checks GDI [gasoline direct injectors] injectors with a pulse tester. Technician B test GDI injectors with an ohmmeter. Who is correct?
B only
Technician A checks a PCV valve by sucking air through it with his mouth. Technician B checks a PCV valve by removing the valve from the grommet in the valve cover and placing his finger over the end of the valve to check for vacuum. Who is correct?
B only
Technician A says a small leak in the air duct between the MAF and the throttle body will not cause a driveability problem. Technician B says a small intake manifold leak in a speed density system will not cause a driveability problem. Who is correct?
B only
Technician A says a vacuum leak will cause an engine to run richer than normal. Technician B says a vacuum leak can cause an engine to detonate. Who is correct?
B only
Technician A says if the EGR valve does not open, the engine may emit excessive amounts of HC. Technician B says if the EGR valve does not open, the engine may detonate on acceleration. Who is correct?
B only
Technician A says in a returnless fuel system, the pressure regulator is mounted on the fuel rail. Technician B says in a returnless fuel system the pressure regulator, fuel sender, and pump assembly are combined in one unit inside the fuel tank. Who is correct?
B only
Technician A says most turbochargers have their own, self-contained, lubrication system. Technician B says a turbocharger should not be operated at an engine oil pressure lower than 30 psi. Who is correct?
B only
Technician A says the AIRB valve directs secondary air either to the intake manifold or to the catalytic converter. Technician B says with the engine at normal operating temperature, the AIR system sometimes goes back into upstream mode with the engine idling. Who is correct?
B only
Technician A says throttle body cleaner may be used to clean the IAC motor internal components. Technician B says on some vehicles, IAC motor damage can occur if the pintle is cleaned with throttle body cleaner. Who is correct?
B only
Technician A says when the ECT sensor detects low engine temperature, the PCM decreases the injection pulse width. Technician B says when the TP sensor detects a sudden increase in throttle angle, the PCM increases the injectors' pulse width. Who is correct?
B only
Technician A uses a low-impedance test light to check for an injector pulse. Technician B uses a noid light to check the injector pulse. Who is correct?
B only
When draining a fuel tank, Technician A drains the fuel into plastic antifreeze containers then caps them tightly to prevent leaks. Technician B drains the fuel into approved gasoline storage containers. Who is correct?
B only
While discussing EGR systems with a differential pressure feedback EGR (DPFE) sensor, Technician A says the DPFE sensor sends a signal to the PCM in relation to intake manifold pressure. Technician B says the PCM can make corrections to the EGR flow if the actual flow does not match the desired flow. Who is correct?
B only
While discussing PFI systems, Technician A says the PCM provides the proper air/fuel ratio by controlling the fuel pressure. Technician B says the PCM provides the proper air/fuel ratio by controlling the injector pulse width. Who is correct?
B only
Before replacing an exhaust system component, Technician A soaks all old connections with a penetrating oil. Technician B checks the old system's routing for critical clearance points. Who is correct?
Both
Crankcase pressure forcing crankcase gases through the clean air hose and into the air cleaner is being discussed. Technician A says the cause may be an excessive amount of blowby. Technician B says the cause may be a restricted PCV valve. Who is correct?
Both
Idle learn procedures for ETC [throttle-by-wire]-equipped vehicles are being discussed. Technician A says the learn or relearn procedure should be completed anytime the PCM has been replaced or updated, or after the throttle body has been cleaned or replaced. Technician B says the system does not need to relearn if the battery has been disconnected. The system will automatically go through the procedure when the engine is restarted.Who is correct?
Both
Quick tests to a GM hot film mass airflow meter on an engine with idling problems are being performed. Technician A taps on the meter lightly with a plastic mallet. Technician B unplugs the meter. Who is correct?
Both
Technician A says a catalytic converter may be tested with a pyrometer. Technician B says a converter may tested using an exhaust gas analyzer. Who is correct?
Both
Technician A says a defective PCV valve may cause rough idle operation. Technician B says the PCV system depends upon a properly sealed engine to perform correctly. Who is correct?
Both
Technician A says cylinder misfiring causes a significant increase in HC emissions. Technician B says a dirty air filter may cause high CO emissions. Who is correct?
Both
Technician A says higher than normal idle speed may be caused by an air-conditioning switch that is always closed. Technician B says higher than normal idle speed may be caused by a defective engine coolant temperature sensor. Who is correct?
Both
Technician A says on some vehicles the fuel pressure is monitored by a fuel rail pressure sensor and the output of the fuel pump is controlled by the PCM through pulse-width modulation. Technician B says all fuel pumps on late-model vehicles are controlled by the PCM according to inputs received on the CAN bus and other specific sensors.Who is correct?
Both
Technician A says pulsation dampers reduce the pressure pulsations caused by the rapid opening and closing of the fuel injectors. Technician B says the damper helps to reduce fuel noise and maintains pressure during engine cooldown. Who is correct?
Both
Technician A says the OBD-II EVAP system leak test monitor will not run if the fuel level is too high. Technician B says the monitor will not run if the fuel level is too low. Who is correct?
Both
Technician A says the TPREL PID is the PCM's closed throttle reference voltage. Technician B says an idle trim relearn procedure should be done whenever a part of the IAC system is replaced or a repair is made to something that affects idle speed. Who is correct?
Both
Technician A says the production of CO2 is directly related to the amount of fuel consumed; therefore, more fuel-efficient engines produce less CO2. Technician B says imposing new CAFE [fuel economy] standards will, in effect, reduce CO2 emissions. Who is correct?
Both
Technician A says there is maximum EGR flow only when the vehicle is at a cruising speed with a very light load. Technician B says instead of an EGR valve many late-model engines use variable valve timing [VVT] to trap some exhaust gases in the combustion chamber. Who is correct?
Both
The AIR system reduces ______. Select one: a. hydrocarbons b. carbon monoxide c. both "hydrocarbons" and "carbon monoxide" d. neither "hydrocarbons" nor "carbon monoxide"
Both
The most important sensor in the fuel management system is _____. Select one: a. MAF [mass airflow] b. MAP [manifold absolute pressure] c. oxygen sensor d. CKP [crankshaft position sensor]
CKP [crankshaft position sensor]
All fuel tanks have a liquid vapor separator.
False
All quick-disconnect fuel line fittings are hand releasable and do not require special tools to disconnect.
False
An ignition misfire can cause excessive carbon monoxide emissions in the exhaust.
False
Creating a large vacuum leak will cause the short-term fuel trim (STFT) and long-term fuel trim (LTFT) to decrease.
False
During closed loop engine mode, injector pulse width is controlled according to predetermined parameters held in the PCM's memory.
False
During its evaporative system integrity test, the canister vent solenoid is open to vent the entire evaporative system.
False
Excessive carbon monoxide [CO] forms when there is not enough O2 to combine with the carbon during combustion.
False
Low CO indicates a lean mixture; as the mixture becomes more lean, HC increases.
False
MAP output is the same as what is measured on a vacuum gauge. When intake vacuum is high, MAP voltage is high.
False
OBD-II systems have only one O2S [oxygen sensor] in the exhaust system, located after the catalytic converter (downstream).
False
Port fuel injected engines require intake manifold heating devices.
False
Static test replacement computers, modules, and computer chips prior to installation.
False
The engine must be at normal operating temperature before the ECT sensor is tested.
False
_____ emissions are caused largely by unburned fuel from the combustion chambers. Select one: a. CO b. HC c. NOX d. CO2
HC
A typical four-gas exhaust analyzer does not measure ____ emissions. Select one: a. CO b. CO2 c. HC d. NOX
NOX
Fuel trim is being discussed. Technician A says a + 12.0 percent LTFT value indicates that the system is running 12 percent richer than normal. Technician B says LTFT should constantly change between positive and negative values when the system is running in closed loop. Who is correct?
Neither
Preliminary checks are being discussed. Technician A says to run specific fuel injection tests first. Technician B says most driveability concerns are caused by PCM-related problems. Who is correct?
Neither
Technician A says TBI systems use top fuel-feeding injectors. Technician B says PFI systems use bottom fuel-feeding injectors. Who is correct?
Neither
All the following are considered harmful gases EXCEPT: Select one: a. HC b. CO c. NOX d. O2
O2
Which of the following gases is NOT considered to be harmful? Select one: a. HC b. CO c. O2 d. NOX
O2
What is the first step in turbocharger inspection? Select one: a. Check the air cleaner for dirty element b. Open the turbine housing at both ends c. Start the engine and listen to the system d. Remove the ducting from the air cleaner to turbo and examine the area
Start the engine and listen to the system
Which of the following statements concerning superchargers is NOT correct? Select one: a. Superchargers must overcome inertia and spin up to speed as the flow of exhaust gas increases b. Superchargers do not require a waste gate to limit boost c. A bypass is designed into the system to allow the supercharger to idle along when extra power is not needed d. Superchargers improve horsepower and torque
Superchargers must overcome inertia and spin up to speed as the flow of exhaust gas increases
A catalytic converter is being tested with a pyrometer. The outlet temperature is 100 degrees Fahrenheit higher than the inlet temperature. What is indicated? Select one: a. The engine is running hot b. The engine is running too lean c. Nothing is happening in the converter d. The converter is operating properly
The converter is operating properly
A scan tool can be used to turn on the fuel pump when the engine is not running.
True
A vacuum gauge may be used to check for a restricted exhaust system.
True
Acoustic supercharging uses the pressure of the air bouncing back and forth between the closed intake valve and incoming air from the plenum to increase the amount of air drawn into the cylinders.
True
An engine in good condition will produce a steady, constant vacuum reading above 15 inches at a warm idle.
True
A CPI [central multiport injection] fuel injection system for a six-cylinder engine has ______. Select one: a. only one injector solenoid b. six poppet nozzles c. a single fuel pressure regulator d. all answers are correct
all answers are correct
A restricted catalytic converter may cause ______. Select one: a. loss of power at high speeds b. stalling after starting c. a drop in engine vacuum as engine rpm increases d. all answers are correct
all answers are correct
A scan tool can be used to diagnose a faulty ______. Select one: a. knock sensor b. EVR solenoid c. EVAP system d. all answers are correct
all answers are correct
An O-ring at the base of a fuel injector ______. Select one: a. seals the injector to its mounting position b. provides thermal insulation to prevent the formation of vapor bubbles c. dampens potentially damaging vibrations d. all answers are correct
all answers are correct
Engine vacuum may be used to operate the ______. Select one: a. power brakes b. cruise control c. air-conditioning system d. all answers are correct
all answers are correct
Fuel injectors may be controlled ______. Select one: a. in pairs or groups b. all at once c. sequentially d. all answers are correct
all answers are correct
The OBD-II EGR system monitor tests the functioning of the EGR system by opening the EGR valve while monitoring the change in ______. Select one: a. STFT b. EGR outlet temperature c. MAP voltage d. all answers are correct
all answers are correct
When cleaning the injectors with a pressurized injector cleaner, prior to starting the engine, ______. Select one: a. remove the fuel pump relay or fuel pump fuse b. pinch off the fuel return hose c. connect the can of cleaner to the Schrader valve on the fuel rail d. all answers are correct
all answers are correct
Which of the following should be checked before proceeding with specific fuel injection and electronic control testing? Select one: a. vacuum lines b. PCV system c. engine coolant level d. all answers are correct
all answers are correct
Fuel injectors are ______. Select one: a. top fuel-feeding devices b. bottom fuel-feeding devices c. both "top fuel-feeding devices" and "bottom fuel-feeding devices" d. neither "top fuel-feeding devices" nor "bottom fuel-feeding devices"
both "top fuel-feeding devices" and "bottom fuel-feeding devices"
Technician A connects a fuel pressure gauge to the Schrader valve on the fuel rail. Technician B connects the gauge to the fuel lines by inserting a tee adapter between the fuel filter and the fuel rail. Who is correct?
both A and B
What class of fire extinguisher should be used on gasoline fires? Select one: a. class A b. class B c. class C d. class D
class B
The longest injector pulse width occurs during ______. Select one: a. deceleration b. idle c. acceleration d. cold starting
cold starting
The first controlled automotive emission was ______. Select one: a. crankcase vapors b. tailpipe emissions [HC and CO] c. NOX d. evaporative emissions
crankcase vapors
Under what conditions is the EGR valve open? Select one: a. starting b. idle [warm engine] c. cruise [warm engine] d. Wide open throttle
cruise [warm engine]
If twenty inches of vacuum is applied to the fuel pressure regulator while the fuel pump is running, the fuel pressure should _____. Select one: a. increase b. decrease c. hold steady d. none of these answers is correct
decrease
A no start/no fuel pressure condition is being diagnosed. When a test light is connected to the pump positive terminal, there is no voltage when the engine is cranked by the starter. What could cause this problem? Select one: a. defective neutral safety switch b. bad fuel pump ground c. defective fuel pressure regulator d. defective fuel pump relay
defective fuel pump relay
The boost pressure of a supercharger is proportional to ______. Select one: a. voltage applied to the boost pressure transducer b. spring tension on the bypass valve c. engine speed d. waste gate position
engine speed
An injector balance test requires an injector pulse tester and a ______.. Select one: a. tachometer b. noid light c. lab scope d. fuel pressure gauge
fuel pressure gauge
What tool is needed to test vacuum-type EGR valves? Select one: a. digital pyrometer b. feeler gauge c. hand vacuum pump d. all answers are correct
hand vacuum pump
A loss of residual fuel pressure immediately after engine shutdown could cause ______. Select one: a. surging b. hard starting c. loss of power at high speed d. excessive emissions
hard starting
What could a leak in the fuel pressure regulator or the fuel pump check valve that allows the fuel pressure to slowly bleed down after engine shut down cause? Select one: a. hard starting b. surging at high speed c. detonation d. excessively lean LTFT
hard starting
In a GDI [gasoline direct injection] system, the tip of the injector is located ______. Select one: a. inside the combustion chamber b. on the throttle body c. in the intake port d. in the intake manifold plenum
inside the combustion chamber
The activity of an O2 sensor is best monitored with a ______. Select one: a. lab scope b. scan tool c. logic probe d. noid light
lab scope
When viewing injector patterns on a lab scope, the injector pulse end with a ______. Select one: a. downward right angle b. first upward spike c. highest upward spike d. last upward spike
last upward spike
While cranking a fuel injected engine and holding the accelerator to the wide-open throttle position, the air/fuel mixture will be ______. Select one: a. lean b. normal c. rich d. stoichiometric
lean
The exhaust gas recirculation system reduces ______. Select one: a. hydrocarbons b. carbon monoxide c. oxides of nitrogen d. all answers are correct
oxides of nitrogen
The throttle body of a port fuel injected engine may include any of the following components EXCEPT: Select one: a. idle air control motor b. single or double bores with throttleplates c. throttle position sensor d. oxygen sensor
oxygen sensor
A high fuel pressure reading is typically caused by a faulty fuel ______. Select one: a. pump b. pressure regulator c. filter d. tank
pressure regulator
The customer complains of poor fuel economy. A five-gas analyzer reveals these measurements at 2,500 rpm: HC = 72 ppm, CO = 3.2%, CO2 = 10.3%, O2 = 0.2%, and NOX = 122 ppm. What is the most likely cause? Select one: a. rich mixture b. lean mixture c. lean misfire d. ignition misfire
rich mixture
A fuel injection system that uses a MAP sensor [manifold absolute pressure] to determine the amount of air entering the engine is called a _____-type injection system. Select one: a. common rail b. mass airflow c. stoichiometric d. speed density
speed density
IAC [idle air control] valves are operated by a ______. Select one: a. vacuum servo b. reversible DC electric motor c. stepper motor d. all answers are correct
stepper motor
A technician is testing a fuel injection system with a scan tool. While the engine is running in closed loop, he loosens a vacuum hose to create a small vacuum leak. Initially the STFT rises and the LTFT remains unchanged. After a few minutes the STFT returns to near zero and the LTFT rises. This test proves that ______.
the system is working normally
A digital EGR valve has up to _____ solenoids. Select one: a. three b. four c. six d. eight
three
An APP [accelerator pedal position] sensor is found on vehicles with ______. Select one: a. automatic transmissions b. automatic traction control c. throttle by wire d. GDI [gasoline direct injection]
throttle by wire
Operation of an O2 sensor is checked with a(n) _____. Select one: a. ammeter b. ohmmeter c. voltmeter d. all answers are correct
voltmeter
What manages turbo output by controlling the amount of exhaust gas entering the turbine housing? Select one: a. waste gate b. turbine seal assembly c. hot wheel d. cold wheel
waste gate
