Advanced Engine Performance Specialist Flashcards

A P0300 random multiple-cylinder misfire combined with a large positive fuel trim most likely results from:

Answer: A large vacuum leak or low fuel pressure affecting all cylinders

A condition affecting all cylinders, such as a vacuum leak or low fuel pressure, causes random misfires with lean trims.

The primary purpose of variable valve timing (VVT) is to:

Answer: Optimize valve events for power, economy, and emissions across RPM

VVT adjusts cam phasing to improve performance, fuel economy, and emissions across the operating range.

A camshaft/crankshaft correlation code (P0016) on a VVT engine often indicates:

Answer: A stretched timing chain or stuck cam phaser/oil control valve

Correlation faults arise when cam timing drifts from crank position due to chain wear or phaser/OCV problems.

When testing an injector with a lab scope, a missing or distorted current 'pintle hump' may indicate:

Answer: A mechanically sticking or worn injector

The pintle hump reflects mechanical movement; its absence or distortion suggests the injector is sticking or worn.

A vehicle in open-loop operation longer than expected after warm-up most likely has:

Answer: A faulty or slow-to-warm O2 sensor or coolant temp sensor

The ECM stays open loop if it doesn't see a hot O2 sensor or correct coolant temperature signal.

Excessive backpressure from a restricted exhaust/converter typically shows up as:

Answer: Loss of power, poor high-speed performance, and low vacuum at RPM

A restriction chokes the engine, causing power loss and falling intake vacuum as RPM increases.

A scan tool data parameter that is 'fixed' or not changing while others update normally usually means:

Answer: A failed sensor, open/short circuit, or a substituted default value

A frozen PID often indicates a circuit fault or a substituted default value reported by the PCM.