How does an induction system vacuum leak affect engine operation?

How does an induction system vacuum leak affect engine operation?

• A. It creates a lean condition, causing rough running, detonation risk, and power loss due to improper metering
• B. It enriches the mixture and increases power
• C. It has no effect on engine operation
• D. It improves throttle response

Answer: (A)

A vacuum leak in the induction system introduces unmetered air into the intake, bypassing the throttle and fuel metering. That extra air makes the air-fuel mixture lean because more air is entering without a corresponding increase in fuel delivery. A lean mixture burns hotter and can cause rough running or misfires, especially at idle or light load. The engine management system will try to compensate by adding fuel, but this compensation has limits, so the symptoms often persist as rough idle and reduced power. Lean mixtures also raise the risk of detonation (knock) under certain conditions, further hindering performance. Because the fuel isn’t being metered to match the extra air, overall power output drops. This is why a vacuum leak doesn’t enrich the mixture or improve throttle response; it disrupts proper metering and leans the mixture, leading to rough operation and power loss.

A vacuum leak in the induction system introduces unmetered air into the intake, bypassing the throttle and fuel metering. That extra air makes the air-fuel mixture lean because more air is entering without a corresponding increase in fuel delivery. A lean mixture burns hotter and can cause rough running or misfires, especially at idle or light load. The engine management system will try to compensate by adding fuel, but this compensation has limits, so the symptoms often persist as rough idle and reduced power. Lean mixtures also raise the risk of detonation (knock) under certain conditions, further hindering performance. Because the fuel isn’t being metered to match the extra air, overall power output drops. This is why a vacuum leak doesn’t enrich the mixture or improve throttle response; it disrupts proper metering and leans the mixture, leading to rough operation and power loss.