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Discussion Starter #1 (Edited)
Irregular revving/idling when A/C works. See video

When A/C is not working engine runs just fine.
However as soon as I turn on the A/C the engine runs OK for a few seconds then revving increases a little for two seconds then goes back to normal, and so on and so forth.
I noticed this fluctuation happens only when the A/C compressor works.
I already changed the idle control valve but problem persists.
Thanks a lot!
 

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Your engine will rev higher because the AC compressor is engaging and putting extra load on it. But it shouldn't be cycling that quickly. Every two seconds is way too fast. I'd guess low pressure, either from a leak or low refrigerant, but it could be the compressor on its way out too.

Do you have cool air coming out?
 

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Vince your Moderator
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Dirty Maf?
 

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your compressor is cycling on an off in the video.
you are low on refrigerant, or your orifice is plugged causing a compressor high pressure causing it to cycle off. or something.

definatly AC needs service. not the idle valve.
 

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To properly diagnose the AC we need gauge readings. It seems that the AC system "safety controls" are the current problem. It could be the low pressure switch or the high pressure switch. It is impossible to tell without some sort of readings. We would also need the ambient temperature at the time of the readings. That is important.

The low pressure switch is there to keep ice from collecting on the evaporator, the high pressure switch is there to keep extreme high pressure from damaging the system components. Pressure is directly related to temperature, by that I mean in the physical science sense where an increase in pressure = an increase in temperature. That is why we need to know the ambient temperature, and why we need to know the pressure on at least the low side which can be measured from the port in the passenger fender under the headlight. The HP port is easy to access from under the hood between the passenger headlight and the radiator.

Sometimes you might be able to "fix" an AC system by simply adding a can of refrigerant, and sometimes not. Refrigerant never goes away unless there is damage to the system.
 
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