2001 Ford Focus Q&A
2001 Ford Focus Question: The idle goes up & down when stopped or moving. It is worse with the ac on.
I would have a qualified shop search for a vacuum leak that could be changing severity depending on engine temp and load conditions. If you are experiencing it does it change when at a stop and shift to reverse or drive? - raiderron
This sounds like it could be a vacuum leak, I have seen the Ford Focus engines get leaks in their PCV hose that goes from the valve cover to the back of the engine many times. If that does not pan out, here are some shops: https://repairpal.com/directory?address=98382&car_brand_names=Ford - dandd