Question about 1985 Chevrolet Chevy

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1985 chevy idles high when defrost is on

Im sure it is a vacum hose, I followed the diagram on the radiator sticker however when in defrost vehicle idles high when on floor heat idle goes down

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  • Brian Johnson Dec 05, 2012

    Stephen is right you should be able to determine if its a leak that way also you could check the iac by watching while someone turned on the defroster and see if it pushes the throttle plate but again you should have the high idle anytime the ac is on if it were the iac

  • Brian Johnson Dec 05, 2012

    it would have high idle on max ac as well as defrost


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Check the vac pod on the heater case and see if the pod is broken or disconnected

Posted on Dec 05, 2012

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Interesting. If it is a vac leak you should be able to plug the line from the intake to kill the leak.
My guess would be the idle speed control is raising the base idle to cover the load the ac compressor would put on the engine.
If the compressor is not working, the computer would not know.

Posted on Dec 05, 2012

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Posted on Jan 02, 2017

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SOURCE: vacuum hose diagram got a

I had this problem with my '93 Ford Probe. What happened was the shaft coming out of the vacuum solenoid was onnected to a plastic arm for the valve that rotated for where you want the air to go. This plastic arm was broken over the years of constant use so I make a small metal one.

Posted on Nov 21, 2008

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SOURCE: my 1981 chevy El Camino V6 3.8L 229 idle gets high

Sounds like a problem with your choke. It may just need to be cleaned (linkages and all). If the choke doesn't close after reaching operating temperature, the engine will rev high. This indicates a choke stuck in the open position. Also, you may need to look for a vacuum leak if cleaning it doesn't fix it. On a 1981 GM product, I'd expect the vacuum hoses to be stiff and cracking.

Posted on May 02, 2009

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SOURCE: 95 chevy g20 idles too high, how do I turn idle down?

i would first check for a vacuum leak because this is considered a newer vehicle and does not have an idle screw, so I would get some "brake kleen" and mist it at each vacuum hose, if the idle changes then change that hose it means there is a leak, and that should sove your problem, if it doesnt , I would then check /replace the idle air control valve as this is the motor that controls the idle

Posted on May 26, 2009

  • 1 Answer

SOURCE: 1995 chevy 4.3 idling at 2300 rpms

1995 S-10 Chevy Blazer just replaced fuel pump now it is idles at 1500 RPM's what should I do.

Posted on Nov 14, 2009

  • 8 Answers

SOURCE: 89 s10 has a high idle

Adjust the idle though the throttle body at the top

Posted on Apr 25, 2010

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Well,of course you can see the diagrams.But there's two pages worth and Fix ya will only let me post 1.Maybe I can post twice off this link?I'll have to give it a shot,usually you can only answer a post once unless there's a reply like you've done.
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Most vehicles had a sticker with a vacuum diagram; try cheaching each hose till you find which one is leaking because that may well be what is causing your rough idle.

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I have the diagram you need. If you send me your email I will scan it off and send it to you.

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it may not be a vacumn leak from a line,check the throttle shaft for movement,for example,i had a 89 1 ton 350 and my throttle shaft was moving around a lot and in order to keep it from idling high,i had to kick the throttle pedal.But also check the idle air control valve,which is the round sensor on the side of the throttle body.

Sep 10, 2009 | 1985 Chevrolet Chevy

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well ther should be a vacume diagram sticker under the hood if it is gone or wore off you can get a haynes manual for that specific car at advance or autozone for about 20 dollars and it will have a diagram in there

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Rough idle at higher rpm smooth

You have a vacume leak somewhere. You can try to listen for it or you can get a can of brake parts cleaner and spray it around the engine. Anywhere there is hoses or connections of any kind. When you find the leak the engine RPM's will increase. If thats not the problem it could be your EGR valve is clogged or your map sensor could be bad. Those things would usually cause a check engine light. Vacume leaks wont. Good luck

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Emission control hose routing

On line. Google 'emissions vacuum routing', you should be able to get an accurate diagram

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