NAPA - National Automotive Parts Association Certified Mechanic Engine Repair and Diagnosis Questions and Answers

Question 1

A customer's vehicle is brought in with the chief complaint of a rattling noise from the front of the engine, particularly noticeable on a cold start-up.
The check engine light is also illuminated.
Which of the following is the MOST likely cause?

Accepted Answer

A worn or failing timing chain and tensioner

Answer

A loose serpentine belt

Answer

A failing water pump bearing

Answer

A cracked exhaust manifold

Question 2

A technician performing a cylinder compression test on a 4-cylinder engine obtains the following readings: Cylinder 1: 150 psi, Cylinder 2: 145 psi, Cylinder 3: 85 psi, Cylinder 4: 155 psi. What is the MOST likely diagnostic conclusion?

Accepted Answer

A significant compression leak in Cylinder 3

Answer

Normal wear on all cylinders

Answer

A blown head gasket between cylinders 1 and 2

Answer

Incorrect valve timing affecting all cylinders

Question 3

A vehicle presents with a low oil pressure warning light that illuminates only at idle when the engine is warm. The oil level is correct. Which of the following is the MOST likely cause?

Accepted Answer

Worn main or connecting rod bearings

Answer

A faulty oil pressure sending unit

Answer

A clogged oil filter

Answer

An overfilled crankcase

Question 4

Which of the following symptoms is LEAST likely to be caused by a failing oxygen (O2) sensor?

Accepted Answer

Engine overheating

Answer

Decreased fuel economy

Answer

Illuminated Check Engine Light

Answer

Rough idling or engine misfires

Question 5

A customer complains of white smoke with a sweet smell coming from the exhaust, along with a gradual loss of coolant without any visible external leaks. The engine has also been running hotter than normal. These symptoms are most indicative of a:

Accepted Answer

Blown head gasket

Answer

Failing catalytic converter

Answer

Cracked radiator

Answer

Stuck open EGR valve

Question 6

During a vehicle inspection, a technician finds metal shavings in the engine oil during a routine oil change. This finding, combined with a customer complaint of a rough idle, most strongly suggests a problem with the:

Accepted Answer

Timing chain

Answer

Oil pump

Answer

Piston rings

Answer

Valve seals

A customer's vehicle is brought in with the chief complaint of a rattling noise from the front of the engine, particularly noticeable on a cold start-up.The check engine light is also illuminated.Which of the following is the MOST likely cause?

A customer's vehicle is brought in with the chief complaint of a rattling noise from the front of the engine, particularly noticeable on a cold start-up.
The check engine light is also illuminated.
Which of the following is the MOST likely cause?