2003 ford focus zx3 2.3 L

May be A/C idle up problem, i would start with a scan to see what the codes are.

So the AC idle up that would be controlled by the idle control valve wouldn't it?

fairly sure with this one that is so but on command from the A/C via the ecu.

So the AC command via the ECU,and what does ecu stand for.I had it scanned and I had a P0302 Misfire cylinder 2.And also a P2274 02 Sensor Signal Lean Bank 1 .Now with the misfire that could be the cause of 02 Sensor running lean couldn't it?

The misfire would set a rich code as unburnt fuel is passing over the O2 sensor, may be a faulty injector or a vacuum leak, ECU is main computer Engine Control unit

But why does it only misfire when AC is on? Could it be a coil it has coil on plugs.What about fuel pressure,or a EGR valve.How do you test the EGR valve? Yeah it only misfires when there is a load on it

Compressor may be seizing up and when on loading the engine up, are there any odd noises, i would try disconnecting the A/c clutch wire and jump it to power, isolate the rest of the system and see if it is the same, if it is it will be a comp problem i feel.

The only noise the compressor makes is when the clutches ingage,but it seems a little loud to me you know the sound but is a pretty loud click I will put it to you this way,if it was running and if you was across the street and it fairly quiet around you could for sure hear it engage.

Did you do the jump wire test? did that make a difference?