5 Common Signs of Engine Trouble You Shouldn’t Ignore

check engine light on vehicle dashboard

The most common signs of engine trouble include warning lights, strange noises, smoke, performance issues, and fluid leaks. Ignoring these symptoms can lead to severe mechanical damage or engine failure.

1. Check Engine Light Turns On

What does the check engine light signal?
The check engine light indicates a problem in the engine control system. It may relate to emissions, ignition, fuel, or sensor issues.

Key details:

  • OBD-II Code: Can be scanned for a fault code (e.g., P0300 for misfire).
  • Severity: A blinking light often signals a serious misfire that may damage the catalytic converter.
  • Action: Use a diagnostic tool immediately or consult a mechanic.

2. Unusual Noises from the Engine

What types of noises suggest engine problems?
Knocking, grinding, hissing, or squealing sounds can signal mechanical failure or component wear.

Examples and causes:

Noise TypeLikely CauseSeverity
KnockingDetonation, worn bearingsHigh
GrindingTiming chain or metal frictionHigh
SquealingWorn serpentine beltMedium
HissingVacuum leak, overheatingMedium to High

Action: Identify noise source early to prevent engine damage.

3. Smoke from Exhaust or Under Hood

Car exhaust smoke

What does engine smoke indicate?
Different smoke colors indicate specific issues:

  • Blue smoke: Oil burning (piston rings or valve seals failure).
  • White smoke: Coolant leak (possible head gasket failure).
  • Black smoke: Fuel-rich mixture (bad injectors, sensor faults).

Engine bay smoke can result from:

  • Overheated components
  • Oil or coolant on hot surfaces

Action: Stop driving immediately and inspect the source.

4. Decreased Engine Performance

How does poor performance reflect engine issues?
Loss of power, rough idling, hesitation, or stalling often signals fuel delivery, ignition, or airflow problems.

Common causes:

  • Faulty spark plugs or ignition coils
  • Dirty air filters or fuel injectors
  • Clogged catalytic converter

Result: Reduced acceleration, poor fuel economy, engine misfires.

5. Leaking Fluids Under the Vehicle

car leaking fluids - Oil leak

What fluid leaks point to engine trouble?
Oil, coolant, or fuel leaks under the engine can indicate seal failure, hose cracks, or gasket wear.

Leak type identifiers:

Fluid ColorLikely FluidSource Location
Brown/BlackEngine oilOil pan, gasket, filter
Green/OrangeCoolantRadiator, hose, water pump
RedTransmission fluidTransmission or cooler line

Action: Inspect undercarriage regularly and repair leaks promptly.