Freestar problems AC
 

Hi!
We need your helpful advice and suggestions on ways to fix our 2004 Freestar.
Here's the problem:
When driving on the highway, at a constant speed, our freestar shutters a little bit only when the AC kicks on. When the AC compressor stops, the shutter goes away. In my opinion, its more than a shutter. The RPMs jump a little like they do when it downshifts.


It should be known that the vehicle, if it were running good, should NOT downshift in this situation.

Please give me any advice as to a possible fix for this problem. I have searched far and wide online and called the dealership. I have not had anyone with an experience like this.

Thanks

Could be the COIL, producing weak spark, or it just need a tune up. Cat could be clog up. Those are the things I checked when mine was doing that.