6 Common Symptoms of an Engine Vacuum Leak

by | Jun 13, 2022

Β There’s one dashboard warning light that most vehicle owners dread – the check engine light! Sometimes, the light takes you completely by surprise because your vehicle didn’t exhibit any signs of malfunction. Other times, you notice something different about its operation and the check engineΒ light is simply confirmation that something is wrong.Β While this important warning light can turn on for several reasons, let’s take a closer look at one malfunction that can lead to an illuminated check engine light – an engine vacuum leak.


What Is an Engine Vacuum Leak?


During the normal operation of your vehicle, air passes to the engine through the throttle body. As it does so, another part … the mass air-flow sensor … measures how much air reaches the engine. This data is then used by the engine control unit (ECU) to determine how much fuel is needed.


When there is a vacuum leak, some air makes its way to the engine via the intake manifold in addition to air entering through the throttle body. Then, the oxygen sensor measures the amount of oxygen in the exhaust gasses. When the amount detected by the oxygen sensor is different from what is measured by the mass air-flow sensor, the check engine light is triggered.


Symptoms of an Engine Vacuum Leak


Often, the cause of an engine vacuum leak is something as simple as a cracked or broken hose. But, other than the check engine light coming on, how do you know when you have a leak?


Typically, an engine vacuum leak will present itself with one or more of these symptoms:


  • Poor gas mileage – An improper air to fuel ratio or inefficient fuel combustion can cause your vehicle to use more fuel than usual. With today’s high gas prices, this is definitely something you want to avoid!
  • Rough idling – With a severe engine vacuum leak, the throttle body will have difficulty maintaining a steady idle speed.
  • Black or white smoke – When the air to fuel ratio is not correct, incomplete fuel combustion occurs and it is often visible through colored exhaust.
  • Delayed or jerky acceleration – When you put the β€˜pedal to the metal’ and your vehicle hesitates, or it accelerates roughly, this is a sign that the air/fuel combination in your vehicle’s engine is not correct.
  • High-pitched noise – As your engine tries to pull air through a leaky hose, you’ll notice a high-pitched squeal. This is one of the easiest symptoms to identify.
  • Illumination of the check engine light – When this warning light is triggered, a code is stored in your engine control unit’s memory. When you take your vehicle to your local auto repair shop, your mechanic can read the code. If the problem is an engine vacuum leak, the code will likely indicate a lean fuel mixture.


Tempe Engine Repairs and Maintenance


If you notice any of these signs of an engine vacuum leak, or your vehicle simply isn’t running as smoothly as it should, we recommend scheduling an appointment at your local repair shop as soon as possible. Your mechanic will diagnose the problem and then provide an estimate for repair. Ultimately, the total cost will depend on the extent of the damage so it’s best to schedule an appointment as soon as you notice that something is amiss.


At Good Works Auto Repair, we believe that preventative maintenance is the best way to protect your investment in your vehicle. When you schedule routine maintenance for your vehicle, small problems can be detected, diagnosed, and fixed before they become bigger and more expensive ones. Simply give us a call or schedule an appointment online today!



And experience QUALITY auto service backed by a 5 year / 60,000 mile warranty! CallΒ 480-894-0018Β or

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Tempe, AZ 85282

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