Rear main. Camshaft plug. Throttle valve. Technician A says the closed coil end of a valve spring should go against the cylinder head.
Technician B says all valve springs use shims to control free spring height. Neither A nor B. For this question, look for the choice that could NOT fit the described situation. All of the following statements are correct when adjusting valve lash on engines with overhead camshaft cylinder heads, EXCEPT:. Shims may be used to make adjustments. Clearance is measured between the camshaft and follower or rocker on most engines.
The follower or rocker must be on the base circle of the camshaft when measuring. The engine must be cold for all engine manufacturers. The surface of the cylinder head has just been machined. What will have to be done to the valve train? Lengthening the push rods. Increasing valve spring tension. Grinding the valve stems. Shim the head.
Engine Block Diagnosis and Repair. A technician hears a knock or thumping at the side of the engine block that is louder when the engine is hot and goes away when the affected cylinder is shorted out. Which of the following could be the cause? Rod bearing. An engine is making a knocking sound that changes with RPM, and the noise disappears while a cylinder is being tested during the cylinder balance test.
Piston Slap. Burnt valve. Technician A says old antifreeze may cause corrosion build-up in the cooling system. Technician B says some original equipment manufacturers OEM recommend that the coolant be changed at specified intervals. Bleeding the air out of the system. Mixing tap water and distilled water.
Mixing the proper ratio of water to coolant. Check the radiator cap for proper fit. Lubrication and Cooling Systems Diagnosis and Repair.
Which of the following customer concerns could be caused by a defective ECT return spring malfunction? Rough idle. Low power.
High idle. Technician A says the voltage required maintaining spark is referred to as the spark line and the duration of the spark line is based on total primary circuit resistance and coil voltage available. Technician B says problems with the burning called fuel propagation will show up within the spark line.
After injecting oil, the pressure remains the same. Which of the following could be the cause? Answer A is wrong. A hole in the piston results in a significant leak and no compression in the cylinder.
Answer B is correct. This second or wet compression test increases compression if the engine has worn piston rings by increasing the seal between the rings and the cylinder wall. If there is little or no change in compression after adding engine oil, the engine has a bad valve, typically the exhaust valve. Answer C is wrong. If cylinder compression increases after adding a teaspoon or two of engine oil, the piston rings have worn.
Answer D is wrong. When the other cylinders are within specifications, and two adjacent cylinders on the same bank are low, suspect a faulty head gasket. One spark plug's ceramic insulator is longer than the others. Which of the following is correct?
Spark plugs have different heat ranges and thread lengths. Answer B is wrong. A spark plug must be hot enough to prevent fouling, yet cool enough to avoid pre-ignition or detonation. A hot spark plug self cleans better than a cold plug, but a cold plug is better at preventing pre-ignition.
Answer D is correct. A hot plug is generally longer than a cold plug. A spark plug with a high heat range runs cleaner but can cause ping, detonation, and pre-ignition problems. Always use the right spark plug. Manufacturers' spend a great deal of time choosing the right spark plug for their engine. Answer D is correct. Air pockets form after draining the engine's coolant.
Some vehicles are more prone to this problem than others. Oil burning in the combustion chamber results in blue-gray exhaust. Coolant entering the combustion chamber results in white-colored exhaust. Answer C is correct. A rich air-fuel ratio causes black-colored exhaust. Answer D is wrong. A rich air-fuel ratio also results in high HC's and black sooty deposits around the tailpipe. A stuck closed PCV valve causes excessive crankcase pressure. A stuck open PCV valve or leaking hose results a rough idle and drivability issues.
A cylinder power balance test indicates two adjacent cylinders are underperforming. Which of the following is causing this test result? A faulty fuel injector will only affect the cylinder it services.
Crossed ignition wires affect two adjacent cylinders. Worn piston rings affect all of the engine's cylinders. A cylinder power balance test compares each cylinder's effectiveness with the others.
A leaking or blown head gasket leaks compression between the two adjacent cylinders.
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