What can happen if the EGR valve vacuum hose is disconnected?

Among the disadvantages of combustion engines is the accumulation of pressure in the contained components. EGR vacuum hoses are used to release the pressure and enable the process of combustion to expel exhaust in the right way.

EGR vacuum hoses, like any other component, are subjected to debris, dirt, high heat, gunk, and other factors that make parts break or wear out.

When they break, they start leaking or become disconnected, and they may cause mechanical failures, ranging from total system shutdown to engine misfires.

Most automotive manufacturers and certified mechanics recommend that the EGR vacuum hoses be inspected every time you change your car’s engine oil or during every tune-up.

The disconnection of an EGR vacuum hose affects the efficiency and stability of the engine. When it leaks, it can make the EGR valve not open, increase the emission of harmful gases and also cause overheating in the engine.

Below are some of the performance problems that are caused by the disconnection of the EGR vacuum hose:

  • Hesitation
  • Low power
  • Poor brakes performance (on power brakes)
  • Stalling
  • Stumbling
  • Poor acceleration
  • Low idle or high idle depending on the model of the vehicle
  • Backfiring
  • Poor fuel economy
  • Hard starting
  • Misfiring (sometimes random)
  • Rough idle

It should be noted that the above-listed symptoms can be caused by other issues and not necessarily a leaking ERG vacuum hose. For instance, problems in ignition timing, bad compression, or a faulty ERG valve can as well cause some of the symptoms.

What can happen to an engine if you drive with a disconnected vacuum hose?

The most common fault in the EGR vacuum hose system is a leak. If the system is leaking, your vehicle efficiency will reduce significantly. In addition, some other parts of the vehicle that depend on the vacuum hose will not work as required if the vacuum is not working.

These parts include especially the diesel particulate filter (DPF) because the number of particulates will increase determining the DPF to get clogged faster than usual.

Below are the safety concerns, symptoms, and signs of driving a vehicle with a leaking EGR vacuum hose:

One of the EGR vacuum hose system areas where leakage commonly occurs is the vacuum lines. The rubber may crack or get old in the vacuum lines and fall off the system itself over time. You should get a mechanic to replace them for you if they become cracked or start leaking.

One of the signs of leakage in the system is a sound emanating from the vehicle engine area when the vehicle is moving. Another sign is problems with the accelerator or a higher idling speed. If you experience such symptoms, either separately or together, you should visit a mechanic and have the vacuum system repaired.

Another common sign of leakage in the EGR vacuum hose system is the Check Engine Light notification. Whenever the Check Engine Light comes on, you should take your car to a mechanic to have the EGR inspected. It is good to have the car checked because other reasons can make the light come on.

One major problem that is brought about by the EGR vacuum leakage is low fuel efficiency and power loss by the vehicle. You will find yourself re-filling the fuel tank more after shorter intervals of time, and the car may fail to accelerate properly.

Fixing an EGR vacuum leak requires a professional mechanic. This is because the EGR vacuum hose system has very many parts, and therefore it may take time to identify the exact place where the leak is. Fixing it by yourself is not that easy.

You should not drive your car with a disconnected EGR vacuum hose because it makes the engine lose power. This is risky, especially when you are driving down a hill and also if the problem increases as you drive. Any time you experience any of the signs, visit a mechanic and have the EGR vacuum pump checked.

Should an EGR valve hold vacuum?

EGR valve has two primary settings: closed and open. The position can also vary anywhere between the two. During the starting up of the engine, it is closed.

At low speed and during idle time, only a little power is needed, and therefore very little oxygen; hence the ERG valve opens gradually.

It can open up to ninety percent when idle. However, as power and torque requirement increases, for example, when the vehicle accelerates fully, it closes to enable more oxygen to get into the cylinder.

While the engine loads, the backpressure increases, causing the EGR control valve to trap more vacuum hence making the valve open.

To test a positive-backpressure EGR valve, you are supposed to tune the engine to 2000 RPM when creating the backpressure and then apply a vacuum to the valve.


In conclusion, you should constantly monitor your car closely enough to notice any signs of a disconnected EGR vacuum hose system.

Any time you notice these signs, you should book an appointment with a professional mechanic as soon as possible to have the car inspected because driving a vehicle with a disconnected EGR vacuum is risky.

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