ASE A1- Engine Repair Exam Latest Updated Graded A+

A compression test shows that one cylinder is too low. A leakage test on that cylinder shows that there is excessive leakage. During the test, air could be heard coming from the tailpipe. Which of the following could be the cause? A. Broken piston rings B. Bad head gasket C. Bad exhaust gasket D. An exhaust valve not seating - ANSWER-The correct answer is D. If an exhaust valve is not seating, air will leak from the combustion chamber by way of the valve out to the tailpipe and make an audible sound. Broken rings or a bad head gasket would have air leaking through the oil filler or cooling system. Technician A says that main bearing oil clearance can be checked with plastigage. Technician B says that main bearing oil clearance can be checked with a dial bore gauge. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is C, both technicians are right. Either method can be used to check main bearing oil clearance. Which of the following is NOT a method of correcting excessive valve stem-to-guide clearance? A. Knurling the valve stem B. Knurling the guide C. Reaming for oversize D. Guide replacement - ANSWER-The correct answer is A. The valve stem is hardened and cannot be knurled. A vacuum gauge is connected to the intake manifold of an engine running at idle. The pointer on the gauge fluctuates rapidly but steadies as the engine speed is increased. The test results indicate: A. A leaking intake manifold gasket B. Worn valve guides C. Late ignition timing D. A weak valve spring - ANSWER-The correct answer is B. Worn valve guide could cause the needle to fluctuate rapidly at idle but steady as the engine speed is increased. A leaking intake manifold gasket or late ignition timing would cause a steady low reading. A weak valve spring would cause the gauge needle to fluctuate as engine speed increased. A technician takes a compression reading on a 4-cylinder engine, and gets readings of 140, 135, 135, and 40 psi. Then he preforms a wet compression test, and the readings are almost the same as those in the first test. Technician A says that a burned valve could cause these readings. Technician B says that a broken piston ring could cause these readings. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is A, only technician A is correct. A burned valve will not allow the cylinder to build compression, and the results from wet and dry compression tests will be the same. If piston rings (or worn cylinder walls) were at fault, compression readings from a wet test would exceed dry test results. Technician A says that retarded valve timing can cause high cylinder compression readings. Technician B says that a lean air/fuel mixture can cause a high intake manifold vacuum reading. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is D, neither technician is right. Technician A is wrong because retarded valve timing will cause the valves to open and close at the wrong time, thereby reducing compression and manifold vacuum readings. Retarded valve timing can be caused by a loose timing belt or chain jumping one or more teeth. Technician B is wrong because a low but steady manifold vacuum reading may be caused by a lean air/fuel mixture. Air leaks or vacuum leaks can cause a lean condition and are common causes of rough idle, hesitation, stalling and hard starting. If the mixture is artificially enriched by injecting propane into the induction system, and engine running lean should speed up and the vacuum reading should rise. An engine is being rebuilt and the crankshaft connecting rod journals have been ground undersize. Specifications show that the original connecting rod journal size was 2.1228-in. 2.1236-in. If the journals now measure 2.1032-in., what size bearings should be used? A. 0.001-in. undersize B. 0.010-in. undersize C. 0.020-in. undersize D. 0.030-in. undersize - ANSWER-The correct answer is C. Adding 0.020 to 2.1032 is 2.1232, which is right in the middle of the standard specifications, so 0.020-in. undersize bearings should be used. Camshaft lift is defined as: A. the distance the valves are open B. the height of the lobes on the camshaft C. the time the valves stay closed