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Q: The idle goes up & down when stopped or moving. It is worse with the ac on. on 2001 Ford Focus

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Have replaced the idle air control valve twoce with only tempory relief. Also cleaned throttle body giving temp relief. No engine light ever comes on. What signales the throtle body to increase rpm at idle position & no pressure on the gas pedal.
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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:
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?
When at a stop often the idle usually returns to 600 rpm after 20 seconds. But sometimes go up & down while stopped.
Ok, I would still suspect a vacuum leak, sometimes they can be intermittent. Have a qualified shop look at it since it sounds like it happens on a regular basis and they should use a "mechanics ear" to try and find it. Good luck.
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