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Why is my car idling so high at start up

I just bought a 2008 jetta less than a month ago and when I start the car it idles high about 1700rpm then gradually goes down down down to about 1000(normal I think) it only does this for all of about 20 or 30 seconds no matter the weather and its usually when I start it for the 1st time each day. What could be the cause and resolution?
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Comments

  • edited November 2010
    If you don't have a check engine light on, this may be normal. Some cars stay on fast idle longer than others. If you are concerned about it, find another '08 Jetta with the same engine and see what it does when started cold. A used car dealer with one in stock will probably let you run this test. If another Jetta with the same engine acts the same way yours does, I would consider it normal.
  • edited November 2010
    Well I took it to a VW repair shop and they said it was a secondary air hose(if I can remember right) and they replaced it but it still idles the same...thanks for your response.
  • edited November 2010
    Was it idling that fast when you bought it? Is it under factory warranty?
  • edited November 2010
    Along That Line Of Thought, Cars Have An Astonishingly Long List Of Engine Sensors, Modules, Actuators, Valves, Etcetera, That Come With The Required Federal 8 Year / 80,000 Mile Warranty.

    To add to Joseph's comments, chances are pretty good that if a car's engine is not running properly during that time period then it's covered.

    CSA
  • edited November 2010
    So did the VW repair shop say that this was abnormal? B/c every car does this when started cold. They basically have an electronic-type of choke where there is a rich fuel mixture to get the car going. Then the idle slowly falls - as you say - over 1/2 to 1 minute or so and approaches its normal warm idle speed.

    What you want to do is find out where the car should be idling when it is completely warmed up. These days the normal range tends to be anywhere between about 650-900 rpm. 1000 is on the high side, and 1700 is certainly on the high side for cold start up.

    So if there is a problem it isn't that car idles higher at start up - its supposed to. Its that it is idling a little high to begin with, both at start up and after warming up. A small vacuum leak can cause that as can a sticking or malfunctioning idle air control valve. Your throttle body and throttle plate are also worth a look.

    The secondary air hose that they referred to is likely a factor mostly when the car is cold so I wouldn't necessarily look there. (And I'm not surprised that it made no difference). Look for an idle issue, not a cold idle issue.
  • edited November 2010
    So I had an appointment this morning with VW and they tested my car and everything is good. Its normal for the 2008 jetta to idle at about 1500rpm at start up after its been sitting for a few hours. The technician also started a few other 2008 jetta's on their lot and confirmed they all do the same thing. He told me that if I ever have any issue the dash with give me some type of indicator. Its still under warranty until the end of 2011 so I'm good :-) Thanks you all for the info.
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