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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; So on warm afternoons when I take my 20 min ride home from work, my idle slowly creeps up. Normally, ...

  1. #1
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    High Idle

    So on warm afternoons when I take my 20 min ride home from work, my idle slowly creeps up. Normally, my idle sits around 850-900. When it is warm out and my car is warmed up, the idle creeps up to almost 1200. In the morning, the idle is fine all the way to work, but once the outside temp goes up my RPM's go up. Anyone else have this problem before?

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    Moderator Cutlass's Avatar
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    check your pcv hoses for cracks/vacuum leaks. thats a common spot for high idle problems

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    Electrical Engineer KMdef9's Avatar
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    Quote Originally Posted by Cutlass View Post
    check your pcv hoses for cracks/vacuum leaks. thats a common spot for high idle problems
    Can dirty MAF can cause this? I imagine it can't hurt to check.


    After those options, I might take a look at the TPS (throttle postion sensor), might be on it's way out.

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    +100 on shitty PCV hoses

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    Spaz is My Mentor SMWS6TA's Avatar
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    Quote Originally Posted by sjsingle1 View Post
    +100 on shitty PCV hoses
    I think me and you are the only ones so opinionated about that.

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    Thanks guys, will check out my PCV and clean my MAF!

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    So I cleaned my MAF and Throttle body. My TPS looked fine. All my hoses looked good. Any other ideas?

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    Smiles for 9.5 Years cammed goat's Avatar
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    How does the IAC look?

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    We just went through this on my brothers cammed camaro, checked PCV system, tried new IAC and TPS, even smoke tested the intake and came up blank. Now we went to the throttle body and it had been ported and drilled for cold start issue with the IAC. We then plugged the drilled hole and the idle went down for a while. So from there we started looking at the butterfly on the throttle body and found it was worn or over ported by the previous owner. New throttle body fixed the problem the first start. So there maybe another point to start at

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    Smiles for 9.5 Years cammed goat's Avatar
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    That gave me a thought...are the throttle blade screws tight?

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    Member 88gtman's Avatar
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    Believe it or not I once had a issue with a loose battery cable on my TA causing a high idle problem.

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    Moderator Cutlass's Avatar
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    Quote Originally Posted by 04torridm6 View Post
    So from there we started looking at the butterfly on the throttle body and found it was worn or over ported by the previous owner.
    I had a similar with my ported TB, except when the guy tightened the blade screws he didn't have the blade centered. So there was a big air gap along the bottom. All I had to do was loosen the screws, snap the TB open a couple times (to center the blade) and tighten the screws.

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    Member Blue_01_Z28's Avatar
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    You would think if the blade was off center it would idle high all the time.

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    Member Blue_01_Z28's Avatar
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    How did you check the hoses? Sometimes it's hard to see one cracked or with a hole. The way I have checked vacuum leaks is with the car on and spraying starter fluid around the hoses I may think are bad. If it's a bad rubber hose or plastic you will find it, the starter fluid will make the car idle higher when it sucks it in.

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    Smiles for 9.5 Years cammed goat's Avatar
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    I've seen folks use starting fluid or a handsoap/water mix.

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    Spaz is My Mentor SMWS6TA's Avatar
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    Mine has always been at about 1000 rpm since I got her. I even have a Frost tune and deleted the crappy pcv so I have no idea why mine idles at 1000-1100 rpm.

    My sig has all mods.

    I've check my TB after reading Cutlass post about P&P TB and mines ok. Besides it does it on my stock TB too. I've checked for vacuum leaks and can't find any I've heard of a possible idle adjustment screw for our TB's but I have never seen or found one that has it yet. If there is one pls post a pic.

    I'm was beginning to think the RPM gauge is just inaccurate but it does seem to idle slightly higher when next to my buddies 99'




    Ninja Edit: I also keep my MAF and TB pretty clean and change my air filter every 2 months.
    Last edited by SMWS6TA; 04-29-2011 at 11:07 AM.
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    Moderator Cutlass's Avatar
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    Quote Originally Posted by SMWS6TA View Post
    I've heard of a possible idle adjustment screw for our TB's but I have never seen or found one that has it yet. If there is one pls post a pic.
    Thats the screw that the TB cam/arm thing rests on at idle. Its the idle bump stop. If you back it out a little bit, it'll close up the TB blade more and might restore the idle back to normal.

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    Quote Originally Posted by Blue_01_Z28 View Post
    How did you check the hoses? Sometimes it's hard to see one cracked or with a hole. The way I have checked vacuum leaks is with the car on and spraying starter fluid around the hoses I may think are bad. If it's a bad rubber hose or plastic you will find it, the starter fluid will make the car idle higher when it sucks it in.
    Yea I just did a visual check of all my hoses. I will have to spray some starter fluid, thanks for the idea! I do not think it has anything to do with my TB since the RPMs only go up when it is hot.

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    Now my car idles high pretty much all of the time. It stays between 1000-1200 usually. At times, it will almost pulse between 900-1100 for a few minutes. What do you think? TPS, MAF, IAC?

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    Electrical Engineer KMdef9's Avatar
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    Quote Originally Posted by 00hawk109 View Post
    Now my car idles high pretty much all of the time. It stays between 1000-1200 usually. At times, it will almost pulse between 900-1100 for a few minutes. What do you think? TPS, MAF, IAC?
    Check 'em, clean 'em.

    Did you check the idle bolt as previously mentioned?

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