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Dealership mechanics don't have any idea or how to fix it. I am a unknowable car mom with a 16 year old ready to drive this car. HELP!

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4  
Can you give us some more detail here? How much is it fluctuating (high/low rpm)? Are there any trouble codes? What type/size of engine? More than likely there is a sensor having issues. I've seen this type of problem in other cars where the Idle Air Control (IAC) is not functioning correctly. Could be the Manifold Absolute Pressure (MAP) going bad or Mass Air Flow (MAF) is dirty. There are a bunch of things which could be causing this, but without further information it will be hard to diagnose. –  Paulster2 Jan 22 at 11:42
    
Ask the mechanics to have a look at the Idle Control Valve. –  Juann Strauss Jul 17 at 12:02

2 Answers 2

Could be as simple as:

  • a blocked fuel filter

  • old fuel

  • vacuum leaks (in some engines)

  • spark timing

  • air/fuel mixture

  • exhaust management

  • if fuel injected, the E.C.M. (electronic control module) can over compensate.

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It may be a leak at the inlet manifold

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I don't think these one line answers are helping you much here on the site. You may want to flesh out your answer with suggestions on how the individual might want to fix the problem if this were the issue. Or perhaps give indications on how to better diagnose the issue. Or give up some clues as to why you think this is their issue. Just trying to help ... and no, I didn't down vote this one either. –  Paulster2 Oct 17 at 0:02
    
Well Paulster2 the reason I suggest it is because I know that a leak at the inlet manifold can cause an engine to hunt. Do you think it would be more helpful to say "Well now, it could be lots of things?" And anyone who is capable of changing the gasket or tightening the nuts on the manifold will know to do that when a leak is suggested. –  dave Oct 17 at 20:00
    
That's good, Dave. You should have included that into your write-up from the get-go. Please remember when you are crafting answers, the answers you give are not only for a regular mechanic, but for the layman as well. By filling out the answer with your reasoning why something is some way, you not only help out this poster, but anyone else who may want to have a complete understanding of the situation. Please remember, most people who will visit this site are not mechanics, they are just trying to understand. You'll have a lot better response to your answers if you post them as such. –  Paulster2 Oct 17 at 20:16

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