CTE Engine Performance & Tuning 2

Question 1

What does a vacuum leak typically cause in an engine management system?

Accepted Answer

Lean air-fuel mixture and rough idle

Answer

A vacuum leak introduces unmetered air, causing a lean condition and unstable idle as the ECU struggles to compensate.

Question 2

Which sensor directly measures the oxygen content in exhaust gases to enable closed-loop fuel control?

Accepted Answer

Oxygen (O2) sensor

Answer

The oxygen sensor signals the ECU whether combustion is rich or lean, enabling closed-loop fuel trim adjustments.

Question 3

Long-term fuel trim (LTFT) of +25% most likely indicates:

Accepted Answer

A lean running condition requiring more fuel

Answer

A high positive LTFT means the ECU is consistently adding fuel to compensate for a persistent lean condition.

Question 4

What is the primary function of a knock sensor in engine management?

Accepted Answer

Detect detonation and signal the ECU to retard timing

Answer

The knock sensor detects detonation vibrations and the ECU retards ignition timing to prevent engine damage.

Question 5

When teaching students about volumetric efficiency (VE), which factor most directly improves VE at high RPM?

Accepted Answer

Optimizing intake and exhaust valve timing and port design

Answer

Optimized valve timing and port velocity allow the cylinder to fill more completely at high RPM, increasing VE.

(CTE) Certified Teacher Career and Technical Education Practice Test