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

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?

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.

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.....

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