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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: Spoonbill on August 21, 2017, 06:41:30 pm

Title: A/c creates high idle
Post by: Spoonbill on August 21, 2017, 06:41:30 pm

So I was sitting the driveway reading some emails and I turned on the a/c and the idle went double as to what it was before I turned the a/c on. It has never done this before. What would cause this to happen????

Title: Re: A/c creates high idle
Post by: bd on August 21, 2017, 07:06:50 pm

Misadjusted idle speed solenoid.

Title: Re: A/c creates high idle
Post by: Spoonbill on August 21, 2017, 07:58:01 pm

That would make it just all of a sudden? Please remember it has only 66,000 original documented miles and all the parts are original except for the tune up I did last November

Title: Re: A/c creates high idle
Post by: Spoonbill on August 21, 2017, 08:08:11 pm

Is this also called iac valve??

Title: Re: A/c creates high idle
Post by: bd on August 21, 2017, 08:13:54 pm

Provide the year, make, model of the truck and the engine/transmission combination.

Title: Re: A/c creates high idle
Post by: Spoonbill on August 21, 2017, 10:50:41 pm

I just put a new iac valve on about 3 months ago. Truck is an 87 r10 305tbi 700r4

Title: Re: A/c creates high idle
Post by: bd on August 21, 2017, 11:11:44 pm

Is the amber Service Engine Soon light coming on?  Are there any stored trouble codes?  Does the A/C work?

Title: Re: A/c creates high idle
Post by: Spoonbill on August 22, 2017, 02:35:05 pm

No warning lights have ever came on. A/c works awesome, it is still the original r-12 one that came on it. It is expensive but well worth it cause it so much colder than 134. To check for codes could I just take it up to autozone and have them hook that hand held scanner up to it?

Title: Re: A/c creates high idle
Post by: bd on August 22, 2017, 03:19:17 pm

That would be a good starting point.  Or, you can retrieve any stored codes yourself using a paperclip; see OBD I code retrieval and decoding (http://forum.73-87chevytrucks.com/smforum/index.php?topic=29949.0).

Does the service engine soon (SES) dash lamp illuminate when you switch on ignition, before starting the engine?

Do you have a digital volt ohmmeter?

Title: Re: A/c creates high idle
Post by: bd on August 22, 2017, 03:58:57 pm

You should also begin to familiarize yourself with the 1987 Light Duty Truck Fuel, Drivability and Emissions (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Fuel_Emissions/X8736_1987_GMC_Light_Duty_Truck_Fuel_and_Emissions_Including_Driveability.pdf) manual.  It is an invaluable, essential tool.

Title: Re: A/c creates high idle
Post by: Spoonbill on August 23, 2017, 08:50:09 pm

Yes it comes on before I start the truck but as soon as started it goes out. I don't know anything about this stuff yet, I'm still in the learning phase so I will let autozone get the codes for me so that I will know it was right