Car Tuning Car Maintenance 5 — Questions and Answers
Question 1: What does 'pinging' or 'knocking' from an engine typically indicate?
- Normal cold-start behavior
- Detonation caused by low-octane fuel or incorrect ignition timing (Correct answer)
- The engine needs an oil change
- A loose heat shield
Correct answer: Detonation caused by low-octane fuel or incorrect ignition timing
Engine knock is caused by uncontrolled combustion (detonation) that can damage pistons and bearings if not corrected.
Question 2: Why is it important to use the correct viscosity motor oil in a turbocharged engine?
- Thicker oil cools the turbo better
- Turbo bearings require proper oil flow rate; wrong viscosity starves or floods them (Correct answer)
- Turbo engines burn more oil so thinner oil is preferred
- Viscosity only matters for naturally aspirated engines
Correct answer: Turbo bearings require proper oil flow rate; wrong viscosity starves or floods them
Turbocharger bearings spin at extremely high RPM and depend on precisely metered oil film; incorrect viscosity disrupts this and accelerates bearing wear.
Question 3: What is the most accurate way to measure remaining brake pad thickness?
- Listen for the wear indicator squeal
- Use a caliper or ruler to measure the pad friction material directly (Correct answer)
- Estimate by looking through the wheel spokes
- Press the brake pedal and note how far it travels
Correct answer: Use a caliper or ruler to measure the pad friction material directly
Direct measurement with a caliper gives exact remaining thickness, while the squeal indicator only triggers near the replacement threshold.
Question 4: Which condition can cause a car's fuel economy to drop noticeably without triggering a check engine light?
- A failed oxygen sensor (always triggers CEL)
- Underinflated tires increasing rolling resistance
- A stuck open thermostat sometimes goes undetected
- Both B and C are correct (Correct answer)
Correct answer: Both B and C are correct
Underinflated tires and a stuck-open thermostat both reduce fuel economy but may not set diagnostic trouble codes.
Question 5: What maintenance step should be performed after installing a new high-flow air filter on a modified engine?
- Reset the ECU and re-tune or check MAF calibration (Correct answer)
- Add a fuel octane booster
- Retorque all engine bolts
- Flush the coolant system
Correct answer: Reset the ECU and re-tune or check MAF calibration
Changing airflow characteristics alters the MAF sensor signal, so a tune or at minimum an ECU reset and adaptation period is needed for proper fueling.
Question 6: What is the danger of overfilling engine oil past the maximum mark on the dipstick?
- The oil warning light will illuminate
- The crankshaft can whip excess oil into foam, causing oil starvation and damage (Correct answer)
- The engine will run cooler than normal
- The exhaust will emit blue smoke only at startup
Correct answer: The crankshaft can whip excess oil into foam, causing oil starvation and damage
Excess oil in the sump gets aerated by the rotating crankshaft, turning it into foam that cannot lubricate bearings effectively.
Question 7: How does flushing old brake fluid improve braking performance?
- Fresh fluid is thicker and creates more pedal feel
- Brake fluid absorbs moisture over time, lowering its boiling point and risking vapor lock (Correct answer)
- New fluid cleans the calipers internally
- Flushing removes air bubbles that accumulate during normal driving
Correct answer: Brake fluid absorbs moisture over time, lowering its boiling point and risking vapor lock
Hygroscopic brake fluid absorbs water from the atmosphere, which dramatically reduces its boiling point and can cause brake fade under heavy use.
Car Tuning Car Maintenance 5
What does 'pinging' or 'knocking' from an engine typically indicate?