ASE A1 Engine Repair Practice Test
1. A vehicle has white-colored exhaust emitting from its tailpipe at all engine speeds. Which of the following is causing this white-colored exhaust?
- A. Worn piston rings.
- B. A leaking head gasket.
- C. Worn valve seals.
- D. A leaking fuel injector.
Answer A is wrong. Worn piston rings result in blow-by and oil burning in the combustion chamber, producing blue/gray exhaust.
Answer B is correct. A leaking head gasket results in a coolant leak from the jacket into the cylinder producing white/gray exhaust.
Answer C is wrong. Leaking valve seals result in oil entering the combustion chamber, especially overnight or after sitting a while. At startup, the engine will produce blue/gray exhaust from this oil burning in the combustion chamber. This symptom may go away after the engine runs a while, but return after the vehicle sits.
Answer D is wrong. A leaking fuel injector results in a rich condition producing excessive hydrocarbons and black exhaust.
2. A vacuum gauge is connected to a port on the intake manifold of an engine with poor performance. The needle on the gauge fluctuates between 15 "hg and 20 "hg vacuum at idle. This vacuum gauge 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. The vacuum is measured inches of mercury vacuum or "hg.
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.
3. New crankshaft bearings are installed after the main bore of an engine block has been line bored. Which of the following is correct?
- A. Use oversized bearings.
- B. Align the oil hole in the bearing to the oil passage in the engine block.
- C. Worn main bearings result in high oil pressure.
- D. Both A and B.
Answer A is wrong. An oversized bearing has the same material thickness on the inside of the bearing facing the crankshaft journal, and more material on the outside facing the bore. Use an oversized bearing after the main bore in the engine block has been line bored.
Answer B is wrong. Make sure the oil passage in the bearing aligns with the oil passage in the engine block when replacing split shell crankshaft bearing inserts.
Answer C is wrong. Excessive internal clearance caused by worn bearings and journals results in low oil pressure.
Answer D is correct. Both A and B are correct.
4. A cylinder power balance test indicates two adjacent cylinders are underperforming. All of the following will cause this problem EXCEPT:
- A. A faulty fuel injector.
- B. Crossed ignition wires.
- C. A cracked cylinder head.
- D. A faulty head gasket.
Answer A is correct. A cylinder power balance test tests each cylinder's effectiveness compared to the others. A faulty fuel injector will only affect the cylinder it services.
Answer B is wrong. Crossed ignition wires affect two adjacent cylinders.
Answer C is wrong. A cracked cylinder head can affect two adjacent cylinders.
Answer D is wrong. A faulty or blown head gasket leaks compression into adjacent cylinders.
5. Technician A says that insufficient hydraulic lifter preload results in excessive valve train noise. Technician B says excessive hydraulic lifter preload results in a high intake manifold vacuum. Who is correct?
- A. Technician A
- B. Technician B
- C. Both A and B
- D. Neither A or B
Answer A is correct. Insufficient lifter preload will cause valve train noise.
Answer B is wrong. Excessive hydraulic lifter preload causes a low intake manifold vacuum.
Answer C is wrong. With a hydraulic lifter, first set the gap to zero lash, and then set the preload.
Answer D is wrong. This initial zero lash adjustment prevents valve tap and is why hydraulic lifters have a quieter operation.