Exam 3: Diagnosing Engine Problems

Technician A says that valvetrain noise will occur at half the speed of engine rpm. Technician B says valvetrain noises coming from inside the timing cover can be caused by a bad timing chain or chain guide. Which technician is correct?

During a compression test, remove all of the _____ _____ so the starter can crank the engine easily.

Carbon has built up in the neck area of a valve. What is the most probable cause?

An engine should produce a minimum of _____ inches of vacuum while cranking, but most engines will produce far more.

Technician A says grounding out a plug wire to a cylinder with a cracked piston will can increase the noise. Technician B says a rod knock will become quieter as its cylinder is grounded. Who is correct?

Technician A says that a compression test can be used to check the condition of the oil control rings. Technician B says that when several cylinders have low compression test readings, this can be due to burned or tight valves. Who is right?

An engine has a crack between a water jacket and an oil gallery. Technician A says that oil will go into the cooling system when the engine is running. Technician B says that coolant will go into the oil when the engine is off. Who is right?

A car has oil smoke from its exhaust during deceleration. Technician A says that bad valve guide seals could be the cause. Technician B says that worn piston rings could be the cause. Who is right?

What two different problems can be pinpointed by looking at the tops of the two pistons shown in Figure here? ​ ​ ​

List several causes of engine overheating.

How many compression strokes (minimum) should the engine crank during a compression test?

When engine idle rises during a cylinder power balance test, what could be the cause?

Technician A says a faulty head gasket can cause the oil to mix with coolant. Technician B says this is called cross fluid contamination. Which technician is correct?

Technician A says that an air-fuel mixture that is too lean can cause burned internal engine parts. Technician B says an overly rich mixture can cause oil wash from cylinder walls. Which technician is correct?

Oil leaks are being discussed. Technician A says a blue lamp can be used to locate an oil leak after a dye has been installed in the crankcase. Technician B says it is a black light that is used. Which technician is correct?

At the end of a spark plug deposit test, what must be done before the engine is accelerated off idle?

If a spark plug is oil-fouled with carbon on only one side, what could be the cause?

When does preignition occur?

Technician A says that an engine that idles rough due to burned valves might run fine at speeds above idle. Technician B says that carbon buildup in a combustion chamber can cause an engine to have higher compression. Who is right?

Technician A says carbon removal additives can damage the muffler. Technician B says if the rpm rises when shorting a cylinder out, it could indicate a vacuum leak. Which technician is correct?