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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; I have a surging problem, about every 3 seconds the car revs slightly. with the IAC unplugged, it stops. idles ...

  1. #1
    Member JacobLS1's Avatar
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    Surging idle, before and after new IAC valve

    I have a surging problem, about every 3 seconds the car revs slightly. with the IAC unplugged, it stops. idles normal. replace the IAC valve today, and it still surges. i believe the TB had been polished. i cleaned the maf, TB, and IAC opening not too long ago. just surged a little faster.

    There is a ticking coming from the intake, do not know if it is related or not.
    http://imageshack.us/clip/my-videos/526/2x2w.mp4/


    thanks.
    Last edited by JacobLS1; 03-12-2012 at 07:42 PM.

  2. #2
    None Shall Pass Knight's Avatar
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    Sounds like a vacuum leak possibly. Check all the vacuum hoses for cracks or even being disconnected. If you can't narrow it down, you can spray a little starting fluid around different areas, and when the idle raises, check that area.

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    Member JacobLS1's Avatar
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    I've tried that before and nothing happened. so if there is one, its that small.

  4. #4
    None Shall Pass Knight's Avatar
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    Another thing you might check is the wiring for the sensor. Make sure the connections are good, and none of the wiring is pinched, broken, or shorting/grounded.

  5. #5
    The Generals Finest Deviant LS1's Avatar
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    Have you done the TPS and IAC reset? When I was cammed sometimes my car wouldn't grab an idle after I disconnected the battery. I would reset the TPS and IAC and the car would idle fine.

    You unplug both the TPS and IAC. Key the car to the ON positiong. Don't start it. Wait 30 seconds, key off. Plug the sensors back in and start the car.

    When you're adjusting the TB set screw to get your IAC counts into the right range you have to do this each time. Perhaps yours is slightly off and just needs to be relearned.

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    Moderator 35th-ANV-SS's Avatar
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    Another thing to consider is that new parts do not always equate to good parts.

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    Electrical Engineer KMdef9's Avatar
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    Quote Originally Posted by 35th-ANV-SS View Post
    Another thing to consider is that new parts do not always equate to good parts.
    This, I got a new iac for my Jeep and it wouldn't bring the idle down, even after the reset it didn't work. Ended up with a different manufacturer to get it working normally.

  8. #8
    Member JacobLS1's Avatar
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    Tried resetting the iac and tps. Cleaned the iac port, and plug. Cant see any physical damage in the wires.

    IAC counts??
    Last edited by JacobLS1; 03-13-2012 at 04:12 PM.
    1998 Z28: Bolt-ons, Stage ? 4L60E. 250rwhp@6500Ft (R.I.P 5/1/2013)

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

  9. #9
    Junior Member smokestack's Avatar
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    Quote Originally Posted by JacobLS1 View Post
    Tried resetting the iac and tps. Cleaned the iac port, and plug. Cant see any physical damage in the wires.

    IAC counts??
    Any handheld scanner? We need data lol

  10. #10
    Member JacobLS1's Avatar
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    Like a tech 2? No. I can probably use one at my brothers work. It set off a p0507.

    What kind of info? so when I use the scanner.

    Found this..I think its coolant. Rock hard..
    Attached Images Attached Images

  11. #11
    Smiles for 9.5 Years cammed goat's Avatar
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    I think that is epoxy. I have read some people use epoxy when they port/polish throttle bodies. I think the epoxy is used to fill the IAC hole and bypasses it.

  12. #12
    Member JacobLS1's Avatar
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    smelt like coolant.. maybe its the coolant line right under the throttle body. i took it out, in hopes of the IAC getting more air. its more quiet. almost seems more subtle. i also hooked the AIR hose back up, but i don't think it helped. no more noise from the AIR pump though.

  13. #13
    Smiles for 9.5 Years cammed goat's Avatar
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    Was the AIR hose ever disconnected before?

  14. #14
    Member JacobLS1's Avatar
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    Ever since I bought it. EGR was removed. Assumed the AIR pump was as well. Bought it two years ago. Problem started last october.

    Neglected to mention. Its only when the engine is warm.
    Last edited by JacobLS1; 03-14-2012 at 05:41 AM.

  15. #15
    Member JacobLS1's Avatar
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    Covered the hole in the throttle body, no more surging. The idle still hangs at 1500 in neutral. Few steps closer atleast.

  16. #16
    Smiles for 9.5 Years cammed goat's Avatar
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    Just checked over the net. When was the last time you checked your PCV?

  17. #17
    Member JacobLS1's Avatar
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    Never. Just see if its clogged?

    Pass. side, adjacent to the tb? I don't see anything...Its an ls6 intake, egr was removed. don't know where the occur would be relocated to. There is something running alongside the intake(pass side)
    Last edited by JacobLS1; 03-15-2012 at 06:38 PM.

  18. #18
    Senior Member JayTA98's Avatar
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    make sure the whole hose/pipe that comes out on the left side of the TB is intact. In that tubing is the PCV. I will check that the PCV is moving free, inspect the rubber pieces where it connect to. Check the whole tubing that goes around the back of the intake. There is a rubber Y behind the intake that roots and causes a vaccum leak. Check the elbow that goes to the drivers side valve cover as well. there is a few pieces of plastic that meltdown if are not in the right place and cause a leak too.

  19. #19
    Member JacobLS1's Avatar
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    Quote Originally Posted by JayTA98:2756659
    make sure the whole hose/pipe that comes out on the left side of the TB is intact. In that tubing is the PCV. I will check that the PCV is moving free, inspect the rubber pieces where it connect to. Check the whole tubing that goes around the back of the intake. There is a rubber Y behind the intake that roots and causes a vaccum leak. Check the elbow that goes to the drivers side valve cover as well. there is a few pieces of plastic that meltdown if are not in the right place and cause a leak too.
    So it's probably the bulge that's runs along the pass. side of the intake under the fuel rails. Ill check the whole hose in the morning. Kinda tempted to pull the intake to check the valley anyway.

  20. #20
    Veteran 0rion's Avatar
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    check that pcv hose where it bends to go into the intake.....they like to crack on the backside of that bend.

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