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Being a two-footed driver to keep your engine from stalling is never fun or easy. An unstable or unpredictable idle can be dangerous and difficult to diagnose. Knowing the signs of an intake manifold leak can lead you to the appropriate repair.
Erratic or Unstable Idle
A vacuum leak in the intake manifold allows excessive air to enter the engine that the computer cannot compensate for. Every car is different as to how it will react. This can cause the engine to stall, it can cause a very high idle rpm, or it can cause the idle to constantly rise and fall on its own.
Noises
An intake manifold gasket leaking can cause a hissing noise coming from under the hood due to the extra air being drawn into the engine.
Check Engine Light
Too much air entering the engine from an intake manifold leak can cause the check engine light to come on. Typically this causes a lean code and possibly a misfire, depending on the severity of the leak.
Coolant Loss
Some lower intake manifolds have coolant running through them. If they leak they can cause the coolant to leak onto the ground or into the engine where it can end up in the oil or be burned in the combustion chamber. If coolant has entered the combustion chamber it will come out of the exhaust pipe as white smoke.
