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Surging idle, before and after new IAC valve

This is a discussion on Surging idle, before and after new IAC valve within the General Help forums, part of the LSx Technical Help Section category; yes the PCV is inside that bulge. Check this hose tubing 1st before pulling the intake. I had a bad ...

  1. #21
    Senior Member JayTA98's Avatar
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    Mean Black
    1998 Trans Am

    yes the PCV is inside that bulge. Check this hose tubing 1st before pulling the intake. I had a bad valley cover gasket but I never noticed it until I decided to upgrade the valley cover.

  2. #22
    Member JacobLS1's Avatar
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    Red
    1998 Z28

    Oh. I saw a pic, someone had it right under the tb. I was gonna pull the intake to see if they're ls6 valley covers. Im not sure of I should bother though.
    1998 Z28: Bolt-ons, Stage ? 4L60E. 250rwhp@6500Ft (R.I.P 5/1/2013)

    1998 Mystic Teal Trans Am: Bone stock. (In process)

  3. #23
    Veteran 0rion's Avatar
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    98 Formula
    06 duramax

    right....if it had an ls6 valley cover it would exit under the tb. The pcv on the 98's is right at the top of the valve cover (has a grounding strap going to a bolt up there) and runs to the front and turns to go into the intake. You said earlier you had a "bulge" there.....that's the pcv valve. Check that hose in the bend and make sure you don't have any leaks post MAF on your intake tract. What you're describing definitely sounds like an air metering issue. Vacuum leak or unmetered air after the MAF.

  4. #24
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
    98 T/A w/a little mods...

    Quote Originally Posted by JacobLS1 View Post
    Oh. I saw a pic, someone had it right under the tb. I was gonna pull the intake to see if they're ls6 valley covers. Im not sure of I should bother though.
    Here is what the LS6 VCT looks like installed. Look just right of the throttle body you will see a hose coming from under the intake to the top of my catch can. If it doesn't look exactly like this then you are still using the LS1 VCT.


  5. #25
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
    98 T/A w/a little mods...

    OP one more thing, I'm not saying you don't have a vacuum leak but......in my case I was going nuts last year chasing what I thought was a slight vacuum leak because my car reads 1000 rpm on the tach at idle. I mean I chased everything, TB, TPS & IAC sensors to adjustments to the TB blade screw. Nothing. Then I had an opportunity to get on a dyno to help a guy demo it. We ran sever times and varies speeds and every time it came to idle my tach said 1000 rpm while the computer was reading it at 800 rpm.

    Just saying it may be the tach has worn out over the last 14 yrs

  6. #26
    Member JacobLS1's Avatar
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    Red
    1998 Z28

    Well in drive it idles around 800 and park is 1100, but if i tap the throttle it drops to 8-900. If i'm coasting and put it into neutral, it will hang at 1500. I don't know if its the throttle body having too much gap around the blade, or what. the surging stops if i cover the hole on the blade.

    The PCV valve is in a sort of..rubber sleeve..should i just cut it off?

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