ASE Practice Test (A1: Engine Repair) 3

Question 1

A technician finds that an engine uses 1 quart of oil every 500 miles but has no external leaks and no visible blue smoke from the exhaust. What is the MOST likely cause?

Accepted Answer

Worn valve stem seals leaking oil during deceleration

Answer

Worn valve stem seals typically leak oil during deceleration when intake manifold vacuum is highest, burning oil without producing constant blue smoke. Oil is drawn past the seals into the intake ports and burned in small intermittent puffs that may not be obvious.

Question 2

What is the purpose of crosshatching cylinder walls during honing?

Accepted Answer

To create an oil retention pattern that aids ring seating

Answer

The crosshatch pattern created during honing provides a surface that holds oil during ring break-in and seating. The angled scratches allow piston rings to properly seat against the cylinder wall while providing lubrication during the critical break-in period.

Question 3

A technician performs a cylinder leakage test and finds 35% leakage on cylinder 3. Air can be heard escaping from the air intake. What does this indicate?

Accepted Answer

Leaking intake valve on cylinder 3

Answer

Air escaping from the air intake during a cylinder leakage test indicates a leaking intake valve. The air passes through the open (leaking) intake valve into the intake manifold and can be heard or felt at the throttle body or air filter.

Question 4

When installing a new timing belt on an interference engine, what is the MOST critical step before rotating the engine by hand after installation?

Accepted Answer

Verifying all timing marks are properly aligned

Answer

On an interference engine, valves and pistons occupy the same space at different points in the cycle. Incorrect timing alignment means valves and pistons will collide when the engine rotates, causing catastrophic damage. Verifying all timing marks are aligned before rotation is essential.

Question 5

A technician finds a cracked exhaust manifold on a 4-cylinder engine. The customer asks if it must be replaced immediately. What is the BEST answer?

Accepted Answer

Yes, because exhaust gases can enter the passenger compartment, posing a carbon monoxide hazard

Answer

A cracked exhaust manifold is a serious safety hazard because exhaust gases contain carbon monoxide (CO), which is colorless, odorless, and potentially lethal. Exhaust gases can enter the vehicle cabin through the HVAC system or firewall openings, posing an immediate danger to occupants.