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Old 02-04-2003, 01:04 PM   #1
desi
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Default What does an IDLE STOP SOLENOID do?

I noticed one wire unplugged on my car. Picked up the manual and found out it is the idle stop solenoid. Manual did not give any more info on this. The car is in storage.... What I need to know is what this does, and why it was disconnected? The car was running excellent BTW. Maybe, I should leave it disconnected? You know what they say "if it ain't broke, doin't fix it"

Thanks in advance

:cheers:
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Old 02-04-2003, 01:21 PM   #2
pws69
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Default Re: What does an IDLE STOP SOLENOID do? (desi)

It increases the idle speed when the A/C is turned on.
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Old 02-04-2003, 01:32 PM   #3
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Default Re: What does an IDLE STOP SOLENOID do? (pws69)

:iagree:
Just confirming Paul's correct explanation.
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Old 02-04-2003, 01:34 PM   #4
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Default Re: What does an IDLE STOP SOLENOID do? (pws69)

Quote:
It increases the idle speed when the A/C is turned on.
:iagree: but not in all cases. On my 74 4-speed the idle stop solenoid is used to set the idle during normal running and does nothing to change the idle speed when the air is turned on. This setup allows the carb to close completely when the engine is turned off and was used to combat some of the early emission problems in lean carbureted engines such as dieseling and run-on. Some earlier models used the solenoid to control engine speed when the AC was turned on. I think you have to look at the specific year and application to get the true intent for your car. I've modified my setup so that the carb idle is set with the idle screw and the AC idle is set with the solenoid. I did this by splicing the solenoid in to the AC clutch wiring. I retained the original wire (always hot as long as the ignition is on) so that in the event I ever put another carb on with an electric choke I'll have a power source.


[Modified by vettfixr, 1:35 PM 2/4/2003]
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Old 02-04-2003, 02:32 PM   #5
ED DINAPOLI
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Default Re: What does an IDLE STOP SOLENOID do? (desi)

I am not aware of any late 60's-mid70s Corvette with a increase idle adjustment to compepensate for AC idle drag. I believe that 71 turned on the AC when the ignition was turned off to keep the engine from dieseling.
The main reason for the idle stop, was to reduce hydrocarbons from being emitted. The idle stop closed the carb completly to reduce these emmissions. It also stopped dieseling byreducing the fuel to the combustion chamber.
Ed
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Old 02-04-2003, 03:43 PM   #6
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Default Re: What does an IDLE STOP SOLENOID do? (ED DINAPOLI)

GM used it to act as the idle adjustment for early cars emissions system. The engines were set up to run hotter so they had a tendency to diesel when shut off. The solenoid would have 12volts on anytime the key was in the run position. Once the key is turned off the solenoid retracted to close off any fuel/air into the chambers.

To answer your question: if it doesn't have this problem then don't worry about it. I disconnected mine after I fixed the cooling system and added a 165-degree thermostat.
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Old 02-04-2003, 04:02 PM   #7
desi
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Default Re: What does an IDLE STOP SOLENOID do? (redwingvette)

Great info guys. thanks. So this is strictly to avoid dieseling the engine, in my case because I don't have AC. BTW, the original owner did install a 165 deg theromstat (which I find a little cooler because the car does not cross 180 at all). I've only had the car for a few months so far. Once I take the it out in spring, I will switch to 180 thermostat and if there is a problem with dieseling.....now I know where to look for answers.
Thanks a bunch. :cheers:
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Old 02-04-2003, 05:10 PM   #8
Chuck Gongloff
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Default Re: What does an IDLE STOP SOLENOID do? (desi)

In 68 and 69 cars, the idle stop solenoid was wired to the AC to bump up the idle when the AC was turned on. It was also used in other years to prevent dieseling as others have stated.

Here's another little known use of the idle stop solenoid for 68 and 69. It was used with solid lifter big block automatics to bump up the idle when the car was put in "DRIVE" from the neutral or park position.

One of the "holy grails" of Corvette parts is the idle stop solenoid bracket for tripower cars, used on 400 AC cars and 435 cars with auto trans. only. :) Chuck
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Old 02-04-2003, 05:40 PM   #9
ED DINAPOLI
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Default Re: What does an IDLE STOP SOLENOID do? (Chuck Gongloff)

Chuck, Thanks for the correction on the 68-69 solenoid function. I never saw on that worked on AC in that manner. I should have stuck to the 70-74, which I know best. You can always learn something new. :cheers:
Ed
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Old 02-05-2003, 12:36 AM   #10
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Default Re: What does an IDLE STOP SOLENOID do? (ED DINAPOLI)

Quote:
I am not aware of any late 60's-mid70s Corvette with a increase idle adjustment to compepensate for AC idle drag. I believe that 71 turned on the AC when the ignition was turned off to keep the engine from dieseling.
The main reason for the idle stop, was to reduce hydrocarbons from being emitted. The idle stop closed the carb completly to reduce these emmissions. It also stopped dieseling byreducing the fuel to the combustion chamber.
Ed
I do know that on my car (late 70's though), it is used to increase idle speed when AC is on. It does its job too.
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Old 02-05-2003, 12:44 AM   #11
OkeeGuy
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Default Re: What does an IDLE STOP SOLENOID do? (Simon Alexander)

what does it do on my 79 w/air? all of my emissions have been removed...
i thought it was there to bump up the idle when i turned on the a/c so i left it on there...
is that not correct?
do i need it?
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Old 02-05-2003, 08:08 AM   #12
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Default Re: What does an IDLE STOP SOLENOID do? (ED DINAPOLI)

Quote:
I am not aware of any late 60's-mid70s Corvette with a increase idle adjustment to compepensate for AC idle drag. I believe that 71 turned on the AC when the ignition was turned off to keep the engine from dieseling.
The main reason for the idle stop, was to reduce hydrocarbons from being emitted. The idle stop closed the carb completly to reduce these emmissions. It also stopped dieseling byreducing the fuel to the combustion chamber.
Ed
:iagree: :withstupid:
John
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Old 02-05-2003, 08:08 AM
 
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1973, 81, ac, adjustment, c4, car, control, corvette, gm, idle, solemoid, solenoid, stop, switch, vacuum, wired


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