I drive a Toyota Corolla S, 2006 model, which had a mileage of 106,000 kilometers. Recently I have noticed that while moving, the engine power goes down as soon as I hit the brakes and stalls. I turn off the engine and it restarts again. It happens again immediately after I touch the brakes. What could be the problem?

While there are many potential issues, here is the most common repair for what you are describing.

A running, normally aspirated engine as in your Corolla generates a vacuum. A vacuum leak anywhere in the engine’s intake manifold system will cause rough running and stalling, and will be most problematic as the engine returns to idle.

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Your vehicle’s brake system employs a vacuum booster, which is used to assist the driver when depressing the brake pedal. A rubber hose is connected to the intake manifold and delivers the engine’s vacuum to the brake booster. Also doubling as an engine vacuum storage vessel, this booster exploits that stored engine vacuum to draw or pull on a rubber diaphragm that is attached to the brake pedal system.

While I am over-simplifying it, the vacuum draw on the booster diaphragm is what gives you power brakes. If the booster, rubber diaphragm or system check valve are damaged, this will provide an unwanted path for the engine vacuum to leak out. Thus causing the same thing as an intake manifold leak.

It’s noticeable to you as a stalling condition when braking and the engine is returning to idle.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing “Lou’s Garage” in the subject line.

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