idle falls off when coming to a stop?
10-19-02, 03:14 PM
#1
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idle falls off when coming to a stop?
Can anyone help? This just started. When i come to a stop or just push the clutch in. The idle drops normally and sits at 600 to 650 rpm. Then it drops to almost zero. And then all of a sudden it goes right back to normal idle. Its better with the a/c on, but still does it occasionally. I can feel the gas pedal move down when it picks the idle up. What controls that?
10-20-02, 05:28 PM
#2
Well i have the problem w/ my gsl-se.
The reason why its better w/ the AC on is due to the seperate AC idle controller. Because the AC draws off the engine power, when it is on the engine would die easier. So they have the AC idle, that when the AC is on it idles higher (so it doesnt cause the engine to die).
But i dont know why it does this otherwise.
The reason why its better w/ the AC on is due to the seperate AC idle controller. Because the AC draws off the engine power, when it is on the engine would die easier. So they have the AC idle, that when the AC is on it idles higher (so it doesnt cause the engine to die).
But i dont know why it does this otherwise.
10-20-02, 08:58 PM
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When you run the A/C, there is a diaphragm that is controlled by a servo in the rat's nest. It is a black cylindrical item, about 2 inches in diameter and 2 inches tall at the back upper driver's side of the carb. This controlls the fast idle needed for the A/C. When the A/C is turned on, vacuum is supplied to the diaphragm, which then pulls on the throttle a little bit to open it up more. It is adjusted by the little flat screw in the middle top of it. Further out = faster idle, but dont' go too far, or else it will "hunt" for a fast idle, up and down.
If your idle is dropping way off when you apply the brakes, then perhaps you are leaking vacuum in the brake master cylinder circuit. Does it happen anytime you apply the brakes? Or only when you are stopping? Are you stopping really rapidly when it happens? If so, perhaps your idle mixture needs adjustment, as sometimes in some carbs the idle mixture gets off when the gas is sloshed in the float bowl, and under hard braking it will all go forward. This would be more pronounced if the float level was too low, but idle mixture adjustment should help to correct for this I think. So check the idle mixture, then idle speed adjustment. (Actually, the two go hand in hand. Follow the procedure in the Haynes manual and you can't go wrong.)
But the first thing I would do is look for a vacuum leak, especially with the application of the brakes. There is also that dash pot on the throttle stop that is supposed to slow down the rate the throttle closes, you might check that too.
Good luck
If your idle is dropping way off when you apply the brakes, then perhaps you are leaking vacuum in the brake master cylinder circuit. Does it happen anytime you apply the brakes? Or only when you are stopping? Are you stopping really rapidly when it happens? If so, perhaps your idle mixture needs adjustment, as sometimes in some carbs the idle mixture gets off when the gas is sloshed in the float bowl, and under hard braking it will all go forward. This would be more pronounced if the float level was too low, but idle mixture adjustment should help to correct for this I think. So check the idle mixture, then idle speed adjustment. (Actually, the two go hand in hand. Follow the procedure in the Haynes manual and you can't go wrong.)
But the first thing I would do is look for a vacuum leak, especially with the application of the brakes. There is also that dash pot on the throttle stop that is supposed to slow down the rate the throttle closes, you might check that too.
Good luck
10-21-02, 02:57 AM
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Yeah i adjusted the air/fuel mixture screw and the idle went up and was running great. I also checked for a vacuum leak and found the power soleniod was loose in the carb. So i snugged it up and test drove it. It was good for awhile and did the same thing. I also checked the dash pot and it contacts at about 1200rpms. It even does it with the a/c on but the vacuum picks the idle up. Do i need to adjust the a/c vacuum some? Could it be the throttle cable, maybe an adjustment?
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10-21-02, 08:23 AM
#8
Rotary Freak
Originally posted by 1985 gs
Yeah i adjusted the air/fuel mixture screw and the idle went up and was running great. I also checked for a vacuum leak and found the power soleniod was loose in the carb. So i snugged it up and test drove it. It was good for awhile and did the same thing. I also checked the dash pot and it contacts at about 1200rpms. It even does it with the a/c on but the vacuum picks the idle up. Do i need to adjust the a/c vacuum some? Could it be the throttle cable, maybe an adjustment?
Yeah i adjusted the air/fuel mixture screw and the idle went up and was running great. I also checked for a vacuum leak and found the power soleniod was loose in the carb. So i snugged it up and test drove it. It was good for awhile and did the same thing. I also checked the dash pot and it contacts at about 1200rpms. It even does it with the a/c on but the vacuum picks the idle up. Do i need to adjust the a/c vacuum some? Could it be the throttle cable, maybe an adjustment?
the idle mixture basically just acts as if you were holding down the gas a little but doesnt effect the choke.
i really dont know much about the dash pot and other emissions equip on the carb,i'm just know some things from working on my b2000 carb which is half the size with half the **** on it
10-21-02, 07:58 PM
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The dashpot is purely mechanical. It is only supposed to prevent your throttle from closing too fast and thus improve emmsions. It isn't the problem.
Have you tested your shutter valve? Its a common culprit.
Have you tested your shutter valve? Its a common culprit.
10-21-02, 08:36 PM
#10
Rotary Freak
Originally posted by Strider
The dashpot is purely mechanical. It is only supposed to prevent your throttle from closing too fast and thus improve emmsions. It isn't the problem.
Have you tested your shutter valve? Its a common culprit.
The dashpot is purely mechanical. It is only supposed to prevent your throttle from closing too fast and thus improve emmsions. It isn't the problem.
Have you tested your shutter valve? Its a common culprit.
but he would hear that
10-21-02, 09:22 PM
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ioTus has the 13B, 1985GS has just that...you've still got a vacuum leak somewhere...try spraying carb cleaner or some kind of "safe" combustible around the base of the carb and around the rat's nest and see if the idle picks up as you do that...it'll narrow your search somewhat...
conversely PM sterling and rattle his cage...
conversely PM sterling and rattle his cage...
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