Auto Information
10 questions · 7 minutes
What's covered
How a car works, system by system. Combined with Shop Information into a single AI+SI score on the paper test, but separate subtests on the CAT.
The four-stroke cycle
Intake, compression, power, exhaust — 'suck, squeeze, bang, blow.' Intake valve opens and the cylinder fills; both valves close and the piston compresses; the spark plug fires and drives the piston down; the exhaust valve opens and spent gas is pushed out.
Engine components
Pistons move in cylinders. The crankshaft converts that up-and-down motion into rotation. The camshaft opens and closes valves in time with the crank. Compression ratio compares cylinder volume at the bottom of the stroke to the top.
Electrical system
A 12V battery supplies starting current. The starter motor cranks the engine. The alternator recharges the battery once the engine runs. The ignition system delivers high voltage to the spark plugs.
Fuel and air
Fuel injectors (or a carburetor on older engines) mix fuel with air. Rich means too much fuel — black smoke, poor economy. Lean means too much air — overheating and knock. Knock is fuel igniting too early, usually from low octane, bad timing, or carbon buildup.
Cooling and lubrication
Radiator, water pump, thermostat, and coolant carry heat away. Antifreeze raises the boiling point and lowers the freezing point. Oil lubricates, cools, and suspends contaminants; the filter catches debris.
Drivetrain
The clutch (manual) or torque converter (automatic) connects engine to transmission. The transmission selects gear ratios. The driveshaft carries power to the differential, which lets the drive wheels turn at different speeds in a corner.
Brakes and suspension
Disc brakes use a caliper squeezing pads against a rotor; drum brakes push shoes outward. The master cylinder converts pedal force into hydraulic pressure. Springs absorb bumps; shock absorbers damp the bouncing afterward.
Diagnosing by symptom
Blue smoke means burning oil. White smoke means coolant. Black smoke means running rich. Pulling to one side under braking means uneven pad wear or a stuck caliper. Continued bouncing after a bump means worn shocks.
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