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Q: RPM running high in neutral

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Rpm ( tachometer) suddenly started running overly high ( marked 3) , and it will stay like that in neutral.

My car has 200000 miles.
My car has a manual transmission.

A: High idle can be caused from several things...

High idle can be caused from several things. Your Saturn's extremely high idle is likely being caused by air leaking into the intake manifold. It's called a vacuum leak. This can be caused by a hose that has fallen off or deteriorated with age. An intake manifold gasket can also leak, which allows extra air into the engine. The computer senses the extra air, adds fuel to match, and suddenly you have a high idle speed. A problem with the engine coolant temperature sensor can also lead to fast idle if it's mistakenly telling the computer that the engine is very cold. There is also a component called the Idle Air Control (IAC) that the computer uses to meter the correct volume of idle air into the intake manifold. The IAC may be dirty, stuck, or broken from old age. A certified mobile mechanic from YourMechanic can visit your home or office to inspect why your vehicle has a high idle and provide any necessary repairs.

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