ASE Advanced Engine Performance Specialist 3 — Questions and Answers
Question 1: A knock sensor that fails or is disconnected will typically cause the ECM to:
- Advance ignition timing aggressively
- Retard timing to a conservative default (Correct answer)
- Disable the fuel pump
- Increase boost pressure
Correct answer: Retard timing to a conservative default
Without valid knock feedback, the ECM retards timing for protection, often reducing power and economy.
Question 2: On a returnless fuel system, fuel pressure is controlled primarily by:
- A vacuum-referenced regulator on the rail
- The PCM varying pump duty cycle via a driver module (Correct answer)
- A mechanical pump on the camshaft
- The throttle position sensor directly
Correct answer: The PCM varying pump duty cycle via a driver module
Returnless systems commonly use a PCM/fuel pump control module to vary pump speed and maintain target pressure.
Question 3: A misfire that occurs only under load and high RPM, with secondary ignition showing high firing voltage, points to:
- A fouled crankcase breather
- Worn spark plugs or a weak coil under demand (Correct answer)
- A stuck thermostat
- A clogged cabin filter
Correct answer: Worn spark plugs or a weak coil under demand
High required firing voltage under load indicates excessive gap or weak spark from worn plugs/coils.
Question 4: When a scan tool shows the O2 sensor stuck at a high voltage (~0.9V), the condition usually indicates:
- A lean exhaust
- A rich exhaust or biased sensor (Correct answer)
- An open heater circuit only
- Normal cruise operation
Correct answer: A rich exhaust or biased sensor
High O2 voltage corresponds to a rich mixture, though a contaminated/biased sensor can also read high.
Question 5: A volumetric efficiency (VE) calculation is a useful advanced diagnostic to detect:
- A weak battery
- Restricted intake/exhaust or cam timing problems (Correct answer)
- A faulty radio
- Low tire pressure
Correct answer: Restricted intake/exhaust or cam timing problems
Calculated VE compared to expected reveals breathing problems like restrictions or incorrect cam timing.
Question 6: An EVAP system small leak (P0442) is most efficiently located using:
- A compression gauge
- Smoke testing the EVAP system (Correct answer)
- A timing light
- A fuel pressure gauge
Correct answer: Smoke testing the EVAP system
Introducing smoke under low pressure makes the leak visible as escaping smoke.
Question 7: If both short-term and long-term fuel trims are significantly negative across all load ranges, suspect:
- A vacuum leak
- High fuel pressure or a leaking injector (Correct answer)
- A restricted air filter only at idle
- An open thermostat
Correct answer: High fuel pressure or a leaking injector
Negative trims mean the ECM is removing fuel to compensate for an inherently rich condition like high pressure or a leaking injector.
ASE Advanced Engine Performance Specialist 3
A knock sensor that fails or is disconnected will typically cause the ECM to: