Advanced Engine Performance Specialist Flashcards

On a turbocharged engine, a P0234 (overboost) code can be caused by:

Answer: A stuck-closed wastegate or faulty boost control solenoid

If the wastegate stays closed or boost control fails, manifold pressure can exceed the allowed limit.

A MAP-based (speed-density) system calculates airflow using manifold pressure, RPM, and:

Answer: Intake air temperature and engine displacement/VE tables

Speed-density estimates airflow from MAP, RPM, IAT, and stored volumetric efficiency data.

An intermittent misfire with no stored DTC is best captured by:

Answer: Using the scan tool's misfire counters and freeze-frame/recording while driving

Misfire counters and data recording during the event identify the offending cylinder and conditions.

A glazed or contaminated oxygen sensor caused by silicone or coolant will typically:

Answer: Become slow/lazy and skew fuel control

Contamination slows the sensor response, degrading closed-loop fuel control.

When the EGR valve sticks open, the resulting symptom is most commonly:

Answer: Rough idle, stalling, and hesitation

Excess inert exhaust gas at idle dilutes the charge, causing rough running, stalling, and hesitation.

A fuel injector flow/balance test is performed to detect:

Answer: Clogged or leaking injectors causing cylinder imbalance

Balance testing compares pressure drop per injector to reveal restricted or leaking units.

A direct-injection engine with carbon buildup on the intake valves commonly causes:

Answer: Rough idle, misfires, and reduced airflow

Because no fuel washes the intake valves in GDI engines, carbon accumulates and disrupts airflow and combustion.