Exam 29: Symptom-Based Diagnosis

Technician A says that a defective TP sensor can cause the engine to hesitate during acceleration. Technician B says that dirty throttle plate(s) on a port-injected engine could cause hesitation during acceleration. Which technician is correct?

An engine diesels after being shut off. The ignition source for this problem is usually ________.

Technician A says that excessive NO_x exhaust emissions can be due to a defective PCV valve. Technician B says that a too lean air-fuel mixture can cause excessive NO_x exhaust emissions. Which technician is correct?

Which of the following symptoms could be caused by a failing ignition coil?

Technician A says that a rich exhaust could be caused by a hole in the rubber diaphragm of the fuel-pressure regulator on a port-injected engine. Technician B says that a defective spark plug wire can cause the engine computer to supply a too-rich air-fuel mixture. Which technician is correct?

Technician A says that poor fuel economy is usually due to an excessively lean air-fuel mixture. Technician B says that a rich air-fuel mixture can be caused by a defective oxygen sensor. Which technician is correct?

Technician A says that a partially stuck-open EGR valve can cause ping (spark knock) during wide-open throttle engine operation. Technician B says that a partially stuck-open EGR valve could cause the engine to stall while operating at idle speed. Which technician is correct?

Technician A says that a leaking fuel pressure regulator diaphragm can cause run-on.Technician B says that a missing thermostat can cause engine run-on. Which technician is correct?

Technician A says that poor fuel economy can be caused by a defective thermostat. Technician B says that a defective evaporative charcoal canister can cause poor or reduced fuel economy. Which technician is correct?

Technician A says that a stretched (worn) timing chain can cause the engine to lack power at slow speeds. Technician B says that a clogged exhaust system can cause the engine to lack power at high speeds. Which technician is correct?

An engine idles OK but misfires during acceleration. This can be caused by ________.

Technician A says that spark knock (ping or detonation) can be caused by a lean air-fuel mixture. Technician B says that an inoperative cooling fan could cause the engine to spark knock. Which technician is correct?

Technician A says that a too-rich air-fuel mixture can be caused by a defective fuel pressure regulator. Technician B says that a defective fuel pressure regulator can cause a too-lean air-fuel mixture. Which technician is correct?

Technician A says that a slowly cranking engine is usually caused by low battery voltage. Technician B says that a hard-start problem is often caused by excessive fuel. Which technician is correct?

An oxygen sensor has failed low (low voltage output). This will cause the PCM to ________.

A restricted PCV system can cause ________.

Technician A says that a fault in the cooling system can cause an increase in engine operating temperatures, and therefore cause a change in NO_x emissions. Technician B says that advanced ignition timing causes the spark to occur too soon while the piston is coming down on the compression stroke. Which technician is correct?

Technician A says that a vacuum leak can cause a rough idle or stalling. Technician B says that spark knock (ping or detonation) is often caused by a too rich air-fuel mixture or an excessively low engine operating temperature. Which technician is correct?

The chemical abbreviation CO stands for ________, and is formed during the combustion process inside the engine.

Technician A says that a rough idle on a fuel-injected engine can be caused by dirty throttle plates. Technician B says that the wrong PCV valve could cause the engine to idle roughly. Which technician is correct?