Symptoms of a Vacuum Leak in a Car

by Jason Medina
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The internal-combustion engine naturally produces a vacuum while running, and engineers have learned to use this vacuum to control a number of other components on a vehicle. Because this vacuum controls so many different parts pf a car, a vacuum leak can cause a variety of system failures and produces numerous symptoms.

Rough Engine Idle

The classic sign of a car with an engine vacuum leak is a rough engine idle. A vacuum leak causes a disruption of the normal vacuum that is created from a running engine. A vacuum leak alters the vacuum pressure of an engine, which results in a rough engine idle.

Engine Hesitation

Along with a rough engine idle, engine hesitation during acceleration is one of the most common symptoms of an engine vacuum leak. During acceleration, the leaking engine vacuum pressure is more pronounced, which presents itself as a stumbling, or hesitating, engine.

Imprecise Transmission Shifting

Engine vacuum provides a large part of a transmission's operational power, a power that helps to properly shift the transmission gears. An engine vacuum leak can cause weak or imprecise transmission shifting points.

Poor Acceleration

A vehicle with a vacuum leak will often have poor acceleration and reduced engine power. This is due to the escaping engine vacuum that reduces the overall force and pressure produced by the engine during combustion.

Hard Vehicle Starting

Depending on the size and location of a vehicle's vacuum leak, hard vehicle starting is often a symptom of a vacuum leak. By reducing the optimal pressure and vacuum within an operating engine, a vacuum leak can inhibit the action and function of a car's carburetor and/or fuel injection system, which directly impacts vehicle starting.

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