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Join Date: May 2004
Location: Brandon FL
Posts: 371
low idle with A/C on?

My daughter complained about her car stalling when coming to a stop. I drove it that night and had no problems. The next day I did some work on it and I noticed that when the A/C is on, it the idle does drop to sub 500 RPM. I pulled the intake and sprayed in some carb cleaner in the ISV and tested it. It works fine. When the A/C is on the idle should come up? How much?

Thanks for any other suggestions.

Rick

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Rick
99 996C4
06 525XI
87 944S - Sold
77 924 - Sold
Old 08-25-2009, 03:21 PM
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Registered Speed Offender
 
Crazy Horse's Avatar
 
Join Date: Jan 2008
Location: Houston, TX
Posts: 205
Check the AC idle air solenoid

On my car, mounted to the back air cleaner box attachment plate, is an AC idle air solenoid. I know this because it was disconnected when I got the car from the PO. After asking questions on this board, I realized what is was, that it was disconnected and that I needed to reconnect the wires to it. Before, when I turned on the AC, the car would idle about 300-400 rpm lower when the compressor kicked in. Now there is almost no change when the compressor kicks in.

Does your car have this solenoid?
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Crazy Horse
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1989 930

Last edited by Crazy Horse; 08-25-2009 at 04:15 PM.. Reason: Sp
Old 08-25-2009, 04:11 PM
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Redline Racer
 
HondaDustR's Avatar
 
Join Date: Jan 2007
Posts: 2,444
I think that solenoid was only on the early 944's. I think the later ones sent a signal to the DME from the AC relay, or something to signal an idle compensation setting.
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1987 silver 924S made it to 225k mi! Sent to the big garage in the sky
Old 08-25-2009, 05:06 PM
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Join Date: May 2004
Location: Brandon FL
Posts: 371
I disconnected the ISV and the idle goes up to about 1100. If I plug it back in the idle drops and it will stall.....
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Rick
99 996C4
06 525XI
87 944S - Sold
77 924 - Sold
Old 08-25-2009, 05:15 PM
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Proprietoristicly Refined
 
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Join Date: Jul 2001
Location: ~Carefree Highway~
Posts: 5,828
The ICV/ISV valve is not giving the DME a correct signal. You may have vacuum leaks in the in and out hoses or the valve is dirty.

There have been a couple recent posts on how to clean the ICV/ISV or go to www.texasblake.com and see his writeup.

The ISV/ICV replaced the early solenoid.

GL
John_AZ

Old 08-25-2009, 05:19 PM
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