Practice Test Geeks(CPT) Certified Production Technician Practice Test
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Engine Performance & Tuning Flashcards

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

Read the first 7 Engine Performance & Tuning flashcards as text

  1. Which ignition timing condition is most likely to cause engine knock (detonation) under load?

    Answer: Timing too far advanced

    Overly advanced ignition timing causes the air-fuel mixture to ignite too early, resulting in abnormal combustion pressure that causes knock.

  2. A technician finds a crankshaft position sensor signal that drops out at operating temperature. The most likely cause is:

    Answer: Heat-related sensor or wiring failure

    Intermittent signal loss that only occurs at operating temperature is a classic symptom of a heat-sensitive sensor or wiring insulation failure.

  3. What parameter does the mass airflow (MAF) sensor measure to help the ECU calculate fuel delivery?

    Answer: Air density and volume flow rate

    The MAF sensor measures the actual mass of air entering the engine per unit time, which the ECU uses as the primary input for fuel injection pulse width.

  4. When performing a compression test, a cylinder reading significantly lower than the others that improves greatly with a wet test (adding oil) suggests:

    Answer: Worn or stuck piston rings

    Oil temporarily seals worn ring gaps, so a compression increase on the wet test points to ring or cylinder wall wear rather than a valve problem.

  5. A faulty coolant temperature sensor (CTS) stuck at a cold reading will cause the ECU to:

    Answer: Continuously enrich the fuel mixture as if at cold start

    The ECU interprets the cold reading as a perpetual cold-start condition and adds extra fuel enrichment, causing a persistent rich running condition.

  6. Which scan tool data PID is most useful for evaluating catalytic converter efficiency?

    Answer: Downstream O2 sensor activity vs. upstream O2 sensor activity

    A healthy converter shows minimal switching activity on the downstream O2 sensor compared to the constantly switching upstream sensor, indicating efficient oxygen storage.

  7. Detonation in a high-performance engine running on pump gasoline can best be prevented by:

    Answer: Retarding ignition timing or using higher octane fuel

    Retarding timing reduces the propensity for autoignition, and higher octane fuel resists detonation better under high cylinder pressures.