That would be an issue with the idle up control valve.

 

I’ve replaced that. I’ve recently heard it can be caused by low Freon?

 

Low idle with AC on usually means the system that controls idle up to compensate for the drag placed on the engine by the AC compressor is not working right. Whether it is the valve, the wiring, or perhaps a vacuum component of the system. I would need to see a diagram.

low freon usually just means that the AC compressor will turn on/off frequently and only run for short periods; or the AC won't work at all if its low enough.

Idle surge is usually an IAC or vacuum issue.

 

Low idle with AC on usually means the system that controls idle up to compensate for the drag placed on the engine by the AC compressor is not working right. Whether it is the valve, the wiring, or perhaps a vacuum component of the system. I would need to see a diagram.

low freon usually just means that the AC compressor will turn on/off frequently and only run for short periods; or the AC won't work at all if its low enough.

Idle surge is usually an IAC or vacuum issue.

I am starting to think it could be a vacuum issue as the iac valve is in working condition