ASE A1 Engine Repair Practice Test

26. Technician A says camshaft duration is the distance the camshaft's lobe lifts the valve off the valve seat and into the cylinder. Technician B says valve overlap occurs when the intake and exhaust valves remain open simultaneously. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B


Answer A is wrong. Camshaft duration, lift, and overlap are vital to valve timing and engine performance. Camshaft duration refers to time; it affects the valve's opening and closing and how long it stays open. It's measured in degrees of crankshaft rotation.

Answer B is correct. As the engine cycles, there's a time when the intake and exhaust valves remain open simultaneously (valve overlap). Valve overlap is an essential function in valve timing.

Answer C is wrong. The exhaust gases flowing through the exhaust valve and manifold help draw the fresh air-fuel charge through the intake valve and into the combustion chamber. This timing is known as valve overlap.

Answer D is wrong. Measure from the nose to the heel of the cam lobe with an outside micrometer, then deduct the base circle. This results in an accurate measurement of the cam lobe lift.

27. A vacuum test is performed on an engine with a rough idle. The needle on the gauge fluctuates between 15 "hg and 20 "hg vacuum at idle. This reading indicates:

  • A. Late ignition or valve timing.
  • B. A normal condition.
  • C. A sticking valve or misfire.
  • D. A restricted exhaust system.


Answer A is wrong. A gauge that reads a steady low (15 "hg - 20 "hg) indicates late valve or ignition timing, leaking manifold gasket, low compression, leaking carburetor, or a stuck throttle valve.

Answer B is wrong. A gauge that reads steady (17 "hg - 22 "hg) indicates a normal running engine.

Answer C is correct. A gauge that fluctuates between (15 "hg and 20 "hg) indicates a stuck valve or engine misfire.

Answer D is wrong. A gauge needle that drops slowly at idle indicates a clogged or blocked exhaust.

28. A piston's top ring groove gap is too wide. The technician would MOST likely:

  • A. Replace the piston.
  • B. Use oversized rings to repair this piston.
  • C. Use a ring groove cleaner to repair the grooves.
  • D. Use a tapered ring set to repair this piston.


Answer A is correct. If this reading is too much and the gap is too large, replace the damaged piston. The top ring takes the most compression. It causes the ring to slap against and wear the lands in the piston groove.

Answer B is wrong. Installing a larger piston ring would not repair this condition.

Answer C is wrong. Remove carbon from the ring grooves before taking measurements.

Answer D is wrong. Many manufacturers install tapered rings on their pistons. They must be installed in the groove correctly, typically with the dot facing up. Check with the manufacturer's specifications before installing piston rings.

29. A vehicle emits a strong sulfur odor from its tailpipe. The MOST likely cause of this condition is:

  • A. A vacuum leak.
  • B. A faulty head gasket.
  • C. Worn piston rings.
  • D. A rich air-fuel ratio.


Answer A is wrong. A vacuum leak results in a lean air-fuel ratio.

Answer B is wrong. A leaking head gasket can leak coolant from the coolant jacket into the combustion chamber. The vehicle would likely emit white-colored exhaust from its tailpipe.

Answer C is wrong. Worn piston rings allow oil to bypass the seal and burn in the cylinder. Oil burning in the combustion chamber results in blue-gray exhaust from the tailpipe.

Answer D is correct. A rich air-fuel ratio produces black-colored exhaust, soot, and a sulfur odor at the vehicle's tailpipe.

30. A 12-volt automotive battery is being tested. Technician A says the battery's specific gravity indicates its current state of charge. Technician B says that if the battery's voltage falls below 9.6 volts at 70° F, the battery capacity test has failed. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B


Answer A is wrong. A specific gravity test determines the weight of a certain volume of liquid divided by an equal amount of water. A fully charged automotive battery has a specific gravity of 1.265.

Answer B is wrong. The discharge rate is one-half of the battery's cold-cranking rating. Apply this load to the battery for 15 seconds. The battery's voltage must remain above 9.6 volts at 70° F.

Answer C is correct. Both technicians are correct.

Answer D is wrong. The specific gravity of a battery is a good indication of its state of charge. Use a hydrometer and adjust to temperature by adding .004 for every ten degrees above 80° F and subtracting .004 for every 10° below 80° F.