DIAGNOSING CAR PROBLEMS

Diagnosing Car Problems | ACDelco

  
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Car trouble indicators and systems can help you pinpoint minor or major problems with your vehicle. This glossary of terms should help you diagnose car problems, identify what’s going wrong with your vehicle and assist you in letting your technician know exactly what’s been happening.

BRAKE PROBLEMS
DESCRIPTION
 
 
Brake Fade
Stopping distance seems to increase, causing longer braking distance, similar to braking at high speeds.
Brake Pedal Pulsation
Brake pedal fluctuates while brakes are applied.
Grabs
Vehicle has a tendency to move right or left when brakes are applied; brakes engage suddenly when applying steady pressure to brake pedal.
Low Brake Pedal
Brake pedal must be pushed unusually far to engage brakes.

ENGINE PROBLEMS
DESCRIPTION
 
 
Cuts Out
Temporary complete loss of power. Engine quits at sharp, irregular intervals. May occur repeatedly or intermittently. Usually worse under heavy acceleration.
Detonation
Mild to severe pings, usually worse under acceleration and load. Engine makes sharp, metallic knocks that change with throttle opening. Sounds like marbles rattling around.
Dieseling
Engine runs after ignition switch is turned off. Runs unevenly and may make knocking noises.
Hesitation
Momentary lack of response as accelerator is pressed. Can occur at all speeds. Usually most severe when starting from a stop. May cause engine to stall.
Missing
Pulsation or jerking that changes with engine speed. Exhaust has a steady spitting sound at idle or low speed. Not normally felt above 30 mph.
Rough Idle
Engine runs unevenly at idle. Car may also shake.
Sluggish
Engine delivers limited power under load or at high speed. Won’t accelerate as fast as normal. Loses too much speed going up hills. Has less speed than normal.
Spongy
Less-than-anticipated response to increased throttle opening. Little or no increase in speed when accelerator is pushed down to increase cruising speed. Continuing to push pedal down will finally give an increase in speed.
Stall
Engine stops running or dies out. May occur at idle or while driving.
Surge
Vehicle speeds up and slows down with no change on accelerator pedal. Can occur at any speed.

HANDLING &  STEERING PROBLEMS
DESCRIPTION
 
 
Bottoming
Suspension moves to extreme end of travel and hits compression bumpers. Feels like a heavy thud.
Excessive Play
Steering wheel must be turned unusually far before vehicle responds.
Hard Steering
Vehicle difficult to steer, especially during parking situations or when first started.
Pulls
Vehicle moves to one side when steering wheel is released.
Shimmy
Rapid side-to-side motion of both front wheels felt in steering wheel.
Sway/Pitching
Mushy or spongy ride; vehicle takes a long time to recover from bumps in the road.
Vibration
Vehicle shakes.
Wanders
Vehicle meanders, requiring frequent steering adjustments to maintain direction.

ODORS & STAINS
DESCRIPTION
 
 
Antifreeze or Coolant Leak
Sweet odor, usually accompanied by steam from under the hood.
Axle Leaks
Black stains with heavy, thick consistency.
Burning Oil
Thick, heavy odor, sometimes accompanied by smoke from under the hood or from the exhaust.
Coolant Streaks
Yellow, green, pink or orange stains that are lighter and thinner than oil.
Crankcase, Oil or Power-Steering Fluid Leaks
Brownish stains.
Electrical Short
Acrid odor, like burned toast.
Emission
Heavy sulfur odor, like rotten eggs.
Overheated Brakes or Clutch
Burning rubber odor.
Overheating
Hot, metallic odor usually accompanied by antifreeze/coolant odor.
Transmission Oil Leaks
Reddish stains.

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