Help with weird AC/Idle issues

[SAC-CA-Runner]

I have a 99 V6 4Runner with about 191,xxx miles. I've noticed when it gets VERY hot out and I have my AC on that my car will idle weird when I am stopped at a light. My car idles around 500-700rpm with the AC on, but then all of a sudden it will start fluctuating between 400 and 600 rapidly and I will hear this clicking noise coming from underneath my glove box. Then I can hear the air in the vents being forced out at a different rate. Can anyone chime in on what this might be or has this happened to them? Like I said, it only happens when stopped at a light with the AC on in the extreme hot. Thanks.

 

[nevada]

not sure on that year but my 85 has an AC idle up controller(not sure of its actual name)...and its behind the glove box.

its purpose is to raise the engine rpms a bit anytime the ac clutch is active.
maybe yours is faulty. if it indeed has one that is...

 

[snivilous]

I have this happen from time to time, the rpm starts oscillating back and forth. Don't know if it's an issue, I usually just turn the AC off for a second or blip the throttle to make it stop acting retarded

 

[SAC-CA-Runner]

Nevada...I did do a search for that and didn't really see anything. But the IAC came up in the Throttle Body and that would need cleaning. Doesn't explain the ticking under the dash. But I'll clean it next time I service my car (2 weeks).

snivilous...it's weird right? Did it when I lived in CO too. Man I miss living there. JUST moved back to CA and I miss CO sooooooo much. <jealous> If I find a resolution all be sure to let you know.

But keep it coming guys...so far one good post that helped!

 

[twomonkeysayoyo]

not sure on that year but my 85 has an AC idle up controller(not sure of its actual name)...and its behind the glove box.

its purpose is to raise the engine rpms a bit anytime the ac clutch is active.
maybe yours is faulty. if it indeed has one that is...

Could be the compressor clutch going out. This will have the effect of the A/C coming on and off with the oscillations. Maybe it's happening too fast to notice at this point.

 

[Skidmarcx]

Any chance you have access to gauges? Pressure readings will help to diagnose a faulty TXV... among other things too