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high idle

This is a discussion on high idle within the General Help forums, part of the LSx Technical Help Section category; This started happening about a week ago, when i drive for a half hour or more my idle will jump ...

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    Member egod's Avatar
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    high idle

    This started happening about a week ago, when i drive for a half hour or more my idle will jump to about 1200rpm in neutral. Its an m6 and no real mods, just curious what could be causing it. The engine will go below 1200 depending on which gear i choose, its only in neutral. Thanks

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    Spaz is My Mentor SMWS6TA's Avatar
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    I believe that the idle rpms for a stock LS1 with no performance tunes are:

    M6: 800rpm
    A4: 650rpm in park/neutral, 550rpm while in gear

    When's the last time you clean your MAF? or air filter?

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    Member egod's Avatar
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    Not that recent, maybe a year a half ago. I know I was throwing a code about my egr but that has been going on way longer. I guess I'll have to have it read again

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    Possible vacuum leak or the IAC is acting up.

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    Quote Originally Posted by SMWS6TA View Post
    I believe that the idle rpms for a stock LS1 with no performance tunes are:

    M6: 800rpm
    A4: 650rpm in park/neutral, 550rpm while in gear

    When's the last time you clean your MAF? or air filter?
    really?

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    Member egod's Avatar
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    Quote Originally Posted by pajeff02 View Post
    Possible vacuum leak or the IAC is acting up.
    Are you talking about the air temp sensor? I was thinking the iat sensor (what I know it as) cause it's the only thing that makes sense because based on time the only thing that really changes is the temp under the hood. But I never thought it would affect the idle but I guess all kinds of stuff can happen when something is not working properly. I guess I'll try replacing that first.

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    Quote Originally Posted by egod View Post
    Are you talking about the air temp sensor? I was thinking the iat sensor (what I know it as) cause it's the only thing that makes sense because based on time the only thing that really changes is the temp under the hood. But I never thought it would affect the idle but I guess all kinds of stuff can happen when something is not working properly. I guess I'll try replacing that first.

    Idle Air Control valve -- it's on the driver side of the throttle body. It meters incoming air to maintain the correct idle. Check the connections and your fuses (not sure which one without looking) and if they are all good then clean it with a spray throttle body cleaner. See if that makes a difference. No vacuum leaks? How about the PCV hose on the passenger side of the throttle body? Bad EGR?

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    Senior Member Too Fast's Avatar
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    Does it happen only when moving? When these cars get warm, especially on hot days like we've been having suddenly, they can have a high idle only when moving, I think that's normal. But if it is something new to the car, and has a high idle when stopped, I would look for a vacuum leak.

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    Member egod's Avatar
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    I know the egr is no good, at least I know it throws a code. No vaccuum leaks from what I can see. I'll have to check the iac then and make sure that's working properly. It is new to the car and started about a week ago.

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    Spaz is My Mentor SMWS6TA's Avatar
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    Check your IAC like PAJeff saids but also need to clean your MAF too if like you said it's been over a yr.

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    Veteran 0rion's Avatar
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    Quote Originally Posted by pajeff02 View Post
    Possible vacuum leak or the IAC is acting up.
    this.....check those hoses really well for a leak. Pay particular attention to the pcv hose where it bends to go into the intake. They crack on the back side of that bend.

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    Spaz is My Mentor SMWS6TA's Avatar
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    Orion,

    This thread has me think about my car now. When should I replace all the vacuum hoses for the PCV and such? What's their life expectancy? Car's a 98 and I'm pretty damn sure none of the previous owners did anything like that...

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    That's kind of a trick question because it depends on the maintenance of the car and exposer of the hoses. Mine is a 98 and my hoses are still in good shape but I've kept them clean and there's been no oil on them. Just keep an eye on them and when they start looking cracked or weathered go ahead and replace them. That pcv hose tends to break down faster because of the oil vapor that's flowing through it.

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    Spaz is My Mentor SMWS6TA's Avatar
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    thx....may have a weekend project coming up...

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    look in the stickies at the top of this section....there's a pcv conversion thread there that'd be worth looking at while you're doing the hoses.

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    The majority of the PCV hose is plastic tubing so it is really the rubber pieces at the ends that are most prone to fail. My hose was shot at the T/B, but the tubing was still in great shape and just as pliable as the replacement. I replaced the entire thing, but kept the original as a backup. If it ever goes back on the car, I'll try it with a spark plug boot as suggested in another thread.

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