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Thread: what is this

  1. #1
    LX User running strong's Avatar
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    high idle in morning

    My car idles high in the morning. I start it, and the choke sets and idles between 2000 and 3000 rpms. When the engine warms up i tap the pedal and the idle normally goes down to around a little less than 1000. Recently, when i tap the pedal the idle stays at 2k. After about 15 minutes of driving the idle normalizes. I can't hear any air bring sucked into a vacuum line, although I'm not ruling a leak out. When i get paid I'm going to get some carb cleaner and test for a leak, I'll probably clean the carb too. I'm fear that the choke is acting up, although during the day it won't idle like this. Also, after ithe idle normalizes there are no issues with idle even when restarting, even if the choke was set.
    Any ideas before i start testing the vacuum lines?
    Last edited by running strong; 09-25-2013 at 02:47 PM.



  2. #2
    LXi User RAZR's Avatar
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    Re: what is this

    Do a visual check to make sure no vacuum lines have holes or are not connected

  3. #3

    Dr_Snooz's Avatar
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    Re: what is this

    Make sure that your throttle butterfly is opening completely.
    Dr_Snooz

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  4. #4
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    Re: what is this

    That sounds like a vacuum leak for sure...quick start is cheap, just spray it around the area and you'll find it quick.

  5. #5
    LX User running strong's Avatar
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    Re: high idle in morning

    Yea I'm pretty sure it's a vacuum leak now too. It idled high after work today. It only seems to happen when there is moisture in the air. I'm going to go find some starting fluid tomorrow and start spraying. Where should i start? I was thinking around the carb, because of all the vacuum lines that go to it.

  6. #6
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    Re: what is this

    It's that time of year (in the northern hemisphere) getting colder and this problem is fairly common. Check for a vacuum leak in the choke opener to fast idle unloader vacuum circuit. (well that's where my problem was; the choke opener diaphragm leaking)

    This vacuum originates at the choke opener(at a vacuum port in the carb) and this feeds vacuum for the fast idle unloader.
    A leak here will cause your described symptoms, but could also be caused be other problems in the circuit.

    There is also a thermo-valve in the circuit that controls the fast idle unloader. Download the manual to trace this out and you can even follow the step-by-step test guide if you get a vacuum gauge/pump.

  7. #7
    LX User running strong's Avatar
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    Re: what is this

    Quote Originally Posted by g.frost View Post
    It's that time of year (in the northern hemisphere) getting colder and this problem is fairly common. Check for a vacuum leak in the choke opener to fast idle unloader vacuum circuit. (well that's where my problem was; the choke opener diaphragm leaking)

    This vacuum originates at the choke opener(at a vacuum port in the carb) and this feeds vacuum for the fast idle unloader.
    A leak here will cause your described symptoms, but could also be caused be other problems in the circuit.

    There is also a thermo-valve in the circuit that controls the fast idle unloader. Download the manual to trace this out and you can even follow the step-by-step test guide if you get a vacuum gauge/pump.
    I'm going to go out and check for a leak today but i have a couple questions. Do I need to take the air filter housing off?
    I also have starting fluid, so should i start the car and then immediately start spraying, or does the idle have to be low? I don't want to burn down my car. What is the best procedure to using starting fluid to find vacuum leaks?

  8. #8
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    Re: what is this

    It's been a few years since I had to replace my choke opener. You have to get the air filter housing off the carb, but don't need to remove all the connections; only enough to prop it out of the way.
    I would suggest you start the car cold and first observe that the choke opens properly; It should close completely when cold cranking then open partly for the cold fast idle. Let the engine warm up and see if the choke opens fully; straight up vertical. (may need to tap the gas pedal)
    ...if not, there is your problem. clean up all the linkage on the carb while you are in there; it could be the problem as well. You can squirt the starter fluid just a bit into the choke opener diaphragm area for starts, and follow from there. Do download the manual so you can trace out where these vacuum lines go. ...otherwise it is just a bowl of spaghetti.

    Check closely to determine if it is the 'fast idle unloader' cam that is keeping your idle up. This is the linkage around the choke opener pivot. (The fast idle unloader sits behind the choke heater. )

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