So, if your vehicle has, vacuum leaking, the air-fuel ratio, will be too high.

Also, called a “lean” mixture, because of, too much air or too little fuel.

As a result, it may, idle faster than usual, idle roughly, misfire, hesitate, or even stall.

Furthermore, with vacuum leaking, you may find your vehicle; doesn’t accelerate, as well as it typically does. Even more, major leaks, might prevent the engine, from starting at all.

Common Symptoms Of, Engine Vacuum Leaking

Fuel Economy And Emissions

The lean air-fuel ratio, will burn hotter and increase the generation of oxide emissions. So, even if the check engine light isn’t triggered; the vehicle may still, fail emissions testing. Drivers would also note, reduced fuel economy; as the engine controller, attempts to compensate, by adding more fuel. The evaporative emissions control system (EVAP), also depends on vacuum to function. So, a leak in an (EVAP) valve or tubing might set, an emissions diagnostic trouble code (DTC).

Check Engine Light

So, the engine control module (ECM), continuously monitors the environment in the engine. Consequently, by using the (MAP) sensor or (MAF) sensor, among others. Also, the (ECM) modulates, fuel injector pulse, spark timing, and valve timing. If there is a vacuum leak, the (ECM) may be unable to compensate. P0171 and P0174 are common, fuel system lean (DTC).

Oxygen (O2) Sensor

Excess oxygen in the exhaust, also indicates a failure to, achieve the correct air-fuel ratio. As a result, leading to sensor issues or even damage to the catalytic converter.


A cracked or leaking intake manifold, will cause a loud whistling or hissing noise, to be emitted from the engine.

Identifying The Location

Consequently, there are many different methods you can use, to find the source of vacuum leaking. So, it really depends on, what you are comfortable with.

But, Always Start With, A Visual Inspection

So, a visual check is a good way to start. Particularly, with vacuum hoses and tubes. Because, they are exposed to extreme under-hood temperatures and oxygen in the atmosphere. Furthermore, rubber vacuum hoses and plastic vacuum tubes, can become stiff or brittle. As a result, easily cracking or breaking. Similarly, rubber engine intake tubes, can also become brittle; cracking and opening a way for unmetered air. Consequently, physically manipulating these components, with the engine running, might reveal the leak.

Some Of The More Common, Vacuum Test Methods Include:

  • Water Method
  • Carb Cleaner
  • Propane
  • Mechanic’s Stethoscope
  • Smoke Machine

Choose Your Help Topic Below

Vacuum Leak Detection – The Safe Way To Find Vacuum Leaks

Vacuum Leaks – How To Quickly Find Vacuum Leaks ( Not The Safest )

Intake Manifold Leaks – Manifold Leaks Spell Trouble For Your Engine

Vacuum Leak Repair Locations – Common Causes – Common Repairs

Thank You !