Practice Test GeeksASE4 - ASE Automobile Engine Performance Practice Test
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Fuel, Air Induction, and Exhaust Systems Flashcards

6 cards from real ASE4 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 Fuel, Air Induction, and Exhaust Systems flashcards as text

  1. A fuel trim diagnostic shows STFT (short-term fuel trim) swinging widely between +25% and -25%. This most likely indicates:

    Answer: A slow-responding oxygen sensor

    Wide STFT swings indicate the ECM is making large corrections due to a slow or lazy oxygen sensor not providing timely feedback.

  2. A scan tool shows both bank LTFT values at +18%. The MOST likely cause is:

    Answer: A large vacuum leak affecting the entire engine

    Equal positive fuel trims on both banks indicate a global lean condition, which points to a vacuum leak or low fuel pressure affecting the whole engine.

  3. A returnless fuel system maintains fuel pressure without a return line to the tank. The pressure regulator in this system is located:

    Answer: Inside the fuel tank on the pump module

    In a returnless fuel system, the pressure regulator is integrated into the in-tank fuel pump module to regulate pressure at the source.

  4. A catalytic converter efficiency code (P0420) is set. Before replacing the converter, the technician should first:

    Answer: Check for misfires, oil burning, or coolant contamination that could have damaged the converter

    A converter failing efficiency is often caused by an underlying engine problem; repairing those first prevents the new converter from failing again.

  5. A cold engine starts and idles but stalls when the throttle is opened. Fuel pressure is normal. The MOST likely cause is:

    Answer: A dirty or failed mass airflow sensor

    A dirty or failed MAF sensor can cause correct idle (using MAP backup) but stumble on throttle opening when accurate airflow data is needed.

  6. An engine equipped with GDI (Gasoline Direct Injection) commonly develops carbon deposits on intake valves because:

    Answer: Fuel is injected directly into the cylinder and does not wash the intake valves

    In GDI engines, fuel is never sprayed onto the intake valves, so oil and PCV vapors accumulate as carbon without the cleaning effect of port injection.