Exam 3: Diagnosing Engine Problems

Oil consumption problems are being discussed. Technician A says a lack of regular services can cause the oil control rings to plug. Technician B says worn compression rings can cause oil consumption problems. Who is correct?

An engine exhibits a low, steady vacuum reading. This could indicate _____.

If an engine will not turn over in either direction, it could be due to a broken crankshaft.

Technician A says that vacuum readings for an engine with a performance camshaft might be lower at idle. Technician B says that an engine that has worn lower main bearings will have lower oil pressure at freeway speeds. Who is right?

Excessive clearance at a connecting rod bearing journal will cause a rod knock.

What happens to the outside of an exhaust pipe at the point of an internal restriction?

Engine operation is being discussed. Technician A says preignition can cause engine damage. Technician B says carbon deposits on the pistons can increase the compression ratio. Who is correct?

A noise occurs at 1⁄2 crankshaft rpm. Technician A says that this could be a bad lifter. Technician B says that this could be a valve that needs to be adjusted. Who is right?

What other engine part failure sometimes results in a cracked piston?

Technician A says that a cylinder leakage test is better than a compression test for testing the Condition of an engine before installing it in a car. Technician B says that a compression tester is better than a cylinder leakage tester for testing the condition of an engine with a performance camshaft. Who is right?

A roar will be heard through the engine's air intake when the _____ system is restricted.

During a compression test, a cylinder shows lower readings than expected. Technician A squirts a tablespoon of oil into the cylinder and the compression raises. He says this indicates a problem with the rings. Technician B says a running compression test should be about one-quarter of that of a cranking compression test. Which technician is correct?

Highway driving can result in extra fuel and water dilution in the oil.

Vacuum readings will drop approximately 1 inch for each _____ feet above sea level.

An engine has late valve timing. Technician A says that this will cause poor low rpm performance. Technician B says that at higher rpm, engine performance might be acceptable. Who is right?

Comparing premium fuel to regular fuel, the burn time of premium fuel is _____.

Two technicians are discussing compression test results. Technician A says that abnormally low compression in adjacent (neighboring) cylinders most likely indicates a bad head gasket. Technician B says that if the reading on the compression tester goes up after adding oil to the cylinder, the compression rings are probably worn. Who is right?

A rich air-fuel mixture could cause a catalytic converter to overheat and melt.

When a spark plug is disabled and the noise becomes louder, what could this be?

An infrared analyzer can be used to check the radiator for combustion leaks.