Examkin

Question

Difficulty: MediumFuel and Air Intake Systems

When an automotive engine's air filter becomes heavily clogged with dirt and debris, how does this restriction primarily affect the air-fuel mixture entering the combustion chambers?

  1. A
    It admits excess unmetered air, causing the mixture to become excessively lean.
  2. It restricts incoming airflow, causing the mixture to become excessively rich.Answer
  3. C
    It delays the opening of the exhaust valve during the four-stroke cycle.
  4. D
    It forces the fuel pump to deliver lower fuel pressure across the fuel rail.

Answer

It restricts incoming airflow, causing the mixture to become excessively rich.
A severely clogged air filter restricts the volume of fresh air entering the induction system. Because the quantity of air is reduced relative to the amount of fuel delivered, the resulting charge contains an excess of fuel, creating an overly rich air-fuel mixture.

Step-by-Step Solution

1
Analyze the mechanical effect of a clogged air filter on intake airflow.
Dirt buildup in the filter media creates high restriction, significantly decreasing the volume and mass of air drawn into the intake tract.
Air must pass freely through the intake filter to maintain proper mass flow for combustion.
2
Determine the impact of reduced air volume on the air-fuel ratio.
With less air available for the given amount of fuel delivered, the proportion of fuel to air increases, producing a rich mixture.
An air-fuel ratio with too little air (or too much fuel) relative to the stoichiometric ideal is defined as rich.

Key Concept

Air filter restriction and its effect on air-fuel mixture balance
Estimated Time:1m 0s
Rate this question

Topics

Fuel and Air Intake Systems

More questions from this topic