A port-injected engine hesitates on light acceleration and one cylinder shows a lean misfire code. Fuel pressure and spark are within specification. The technician should suspect:
Q 02Component Function
In a mass airflow system, the intake air temperature sensor signal is used by the PCM to:
Q 03Tech A/B
Technician A says a pressure test can reveal a coolant leak not visible when cold. Technician B says a thermostat stuck open can extend open loop operation. Who is right?
Q 04Data-Driven
Voltage drop readings were taken while cranking. These readings indicate:
Test point
Reading
Maximum
Positive cable, battery to starter
0.18 V
0.20 V
Positive battery post to cable clamp
0.02 V
0.10 V
Negative cable, battery to engine block
0.64 V
0.20 V
Starter housing to engine block
0.05 V
0.20 V
Q 05Least Likely / EXCEPT
An engine cranks but will not start, and there is no spark at any cylinder. Which of these is the LEAST likely cause?
Q 06Procedure/Tool
Which procedure most reliably locates a small unmetered air leak downstream of the mass airflow sensor?
Q 07Most Likely
An engine stalls at idle and hesitates on light throttle. Scan data shows the EGR valve reporting open while commanded closed. What is the MOST likely cause?
Q 08Tech A/B
Technician A says clearing codes with a scan tool sets the readiness monitors to complete. Technician B says each monitor must run before the vehicle passes a readiness check. Who is right?
Q 09Scenario-Based
A cylinder 4 misfire appears only after the engine reaches full operating temperature. Moving the coil to cylinder 2 moves the misfire with it. The cause could be:
Q 10Data-Driven
Cranking compression on cylinder 2 is 170 psi. Running compression at idle is 82 psi and rises to 155 psi on a snap throttle. These readings indicate:
Q 11Least Likely / EXCEPT
Any of these could cause blue-gray exhaust smoke EXCEPT:
Q 12Most Likely
A high-mileage engine develops oil seepage at the valve cover and rear main seal, plus oil in the air inlet duct. What is the MOST likely cause?
Q 13Tech A/B
Technician A says an oxygen sensor signal circuit is tested with an ohmmeter. Technician B says an air/fuel ratio sensor switches between 0.1 and 0.9 volt. Who is right?
Q 14Procedure/Tool
Which procedure correctly checks a throttle position sensor for an intermittent open spot?
Q 15Component Function
An automatic drive belt tensioner is designed to:
Q 16Least Likely / EXCEPT
An engine surges at steady highway cruise. Which of these is the LEAST likely cause?
Q 17Scenario-Based
A converter efficiency code is stored. The downstream oxygen sensor signal swings up and down almost identically to the upstream sensor. The cause could be a:
Q 18Tech A/B
Technician A says a blistered white insulator suggests the plug ran too hot. Technician B says wet oily deposits on one plug indicate too high a heat range. Who is right?
Q 19Data-Driven
Long-term fuel trim reads −2% at idle, +9% at 1500 rpm, and +24% at 2500 rpm. Specification is within ±10%. The cause could be a:
Q 20Component Function
A radiator pressure cap raises system pressure in order to:
Q 21Least Likely / EXCEPT
A PCM has been replaced and the engine will not start. Which of these is the LEAST likely cause?
Q 22Procedure/Tool
Which procedure correctly tests an ignition coil primary control circuit for a driver fault?
Q 23Most Likely
Several sensors report implausible values at the same time and the PCM sets multiple unrelated codes. What is the MOST likely cause?
Q 24Tech A/B
Technician A says the purge valve is held open with the engine off to vent vapors. Technician B says the vent valve closes to seal the system for a leak test. Who is right?
Q 25Scenario-Based
A vehicle fails an emissions test for high hydrocarbons. Scan data shows the upstream oxygen sensor switching only twice in ten seconds at 2000 rpm. The cause could be a:
Answers and explanations are revealed after you submit the full test.
0%
0 / 25 CORRECT
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Reading Your Results: A8 Engine Performance, Test 2
This test comes at the same content areas through the scan tool and the
waveform rather than the symptom. More of these questions turn on what a data value actually
proves, on isolating a fault by moving a part, and on reading the emissions systems that most
technicians study last.
If you missed the questions about isolating a fault
Substitution is the fastest test in driveability work, and this test uses it repeatedly. When
a misfire follows a coil to its new cylinder, the coil carries the fault and everything left
behind is cleared in one move. When the misfire stays with the original cylinder, the coil is
proven and the fault is compression, fuel delivery, or that cylinder's driver circuit. The same
logic applies to injectors and to sensors. The value of the test is that it answers one question
cleanly rather than narrowing a list, which is why it belongs early in a diagnosis instead of
after three parts have already been replaced.
If you missed the questions about what scan data proves
A scan tool reports what a module believes, and the gap between belief and reality is where
most of these questions live. An EGR valve reporting open while commanded closed means the
module's expectation and the valve's actual position disagree, so the fault is a stuck valve, a
carboned passage, or a position sensor rather than a control problem. A downstream oxygen sensor
swinging almost identically to the upstream sensor means the converter is not storing oxygen,
because a healthy converter smooths that signal out. Several unrelated sensors reporting
implausible values at once is almost never several failed sensors, it is a shared reference or
ground they all depend on. Ask what the module can actually see before you trust what it is
reporting.
If you missed the questions built on a measurement
Three questions here give you readings, and each is asking whether you know what the number
is describing.
Running compression. Running compression is a different measurement than
cranking compression, not a repeat of it. At idle the throttle is nearly closed so the reading
is a fraction of the cranking figure, and on a snap throttle it should climb sharply as the
cylinder finally gets a full charge. A reading that fails to climb points at a restriction on
the intake side, and one that stays high points at an exhaust that is not clearing.
Fuel trim that grows with load. Trim within limits at idle and climbing past
them at higher engine speed describes delivery falling behind demand, which is the signature
of a supply-side restriction rather than an air leak. The direction the number moves as load
increases is the whole diagnosis.
Cranking voltage drops. A voltage drop is taken across a section of circuit
while it is carrying current, so cranking is exactly when the reading means something. A drop
well above the allowable few tenths on either the insulated or the ground side is resistance
stealing voltage the starter never receives.
If you missed the EXCEPT and LEAST likely questions
Four appear on this test, and the method is the same one that works on the real exam.
Identify what the three real causes share before hunting for the odd one out. On the no-spark
question, three answers all interrupt the primary ignition path or the crank reference the PCM
needs to fire it, and one affects fuel rather than spark. On the blue-gray smoke question, three
answers all give oil a route into the combustion chamber, and one produces a different color
entirely. Naming the shared trait first is faster and far more reliable than working through
four options one at a time.
If both free tests are landing comfortably above 70 percent, the premium A8 tests move into
harder diagnostic scenarios on a 30-minute clock. They also score you by ASE content area and
by question type, and give you the official ASE task number for every question you miss, so
you can take those numbers straight to the study guide instead of rereading a chapter.
The ones you missed are open. Click any other question to see the answer and explanation.
Disclaimer: Study ASE for Free is an independent educational resource and is not affiliated with, endorsed by, sponsored by, or otherwise connected to the National Institute for Automotive Service Excellence (ASE), Prometric, or any official ASE testing center. All practice tests and materials provided on this site are created solely for educational and practice purposes only.
