Engine hunting while aircon is switched on

Hi my dad has got a 1998 Ford Cougar 2.5 V6 and when the aircon is switched on the engine starts to hunt between 750 - 1100 RPM and continues to hunt
while driving until about 2000 RPM giving a jerky feeling, this does disappear above 2000 RPM however.I would be very grateful if anyone could shed some light on this problem. Many thanks in advance for any feedback. Dean
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the air con compressor is switched and controlled by the PCM/ECU maybe its just low(or has none)air con refridgement (R134a) it is 7 years old now, when was it last done?
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Why do you call it Aircon? Are you filipino? Everyone else calls it the A/C, or air conditioning. Southerners call it "Central Air" regaurding a house.
East-
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Dean wrote:

Dirty/worn IAC valve.
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