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poor idle with AC on

when the ac is on the pcm should command the iac to increase the idle. you might have a dirty iac or intake.

is your idle speed low?
 
What are the idle speeds with and without the AC on?
 
when it occurs its starts to bog a little below 1000-700 probably, so yes low, but not consistant. IAC has been cleaned as of a few months ago while checking a different issue, jeep ran better after to. this one is just weird.

I havent had AC on much, but when its full out running and a hot day its more noticeable.
 
Normal idle should only be around 600-700 on a Renix even without the AC. The emissions police dinged me because mine was idling at 900 hot.
 
When your a/c is on, does the compressor spin constantly, or does it cycle on and off? Your a/c system could be undercharged.
 
It would cause a more constant load on the engine. If you are sputtering at idle, I would be thinking more spark plug wires, cap, or even plugs themselves.
 
Though I think it's a tuneup issue, are your vents going from vent to defrost when the idle changes? You're expected idle is higher than normal and the first thing I check in that case is for a vacuum leak and that leak may be getting worse under load. That could cause your vents to mess up.
 
I agree with these two!!! But year is it????

If it 1990 or older, Renix, the grounds may need cleaning badly!!!

It would cause a more constant load on the engine. If you are sputtering at idle, I would be thinking more spark plug wires, cap, or even plugs themselves.

Though I think it's a tuneup issue, are your vents going from vent to defrost when the idle changes?

You're expected idle is higher than normal and the first thing I check in that case is for a vacuum leak and that leak may be getting worse under load. That could cause your vents to mess up.

Could be both!!!! Or all three, vacuum leaks, needs a tune up and grounds cleaned up
 
The AC is just a distraction, unless the belts are squealing. That load just makes the wandering idle more noticable.

4.0 XJ correct idle is 750 rpm

Would undercharged cause the idle to spudder?
 
It will dip below 750 when it's sounds like it's going to shut off. 600 or less maybe, then pick up shortly after. Once driving it's fine.
I need to replace the main grounds from the battery because of another issue. Could this hinder idle with AC on full?
 
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Maybe, if the sensor grounds are seeing back voltage from a poor ground system.
 
i know it might have been far fetched, but i couldnt have hurt to asking while im digging for answers.

with the mileage it has i could see the IAC maybe, but i havent been able to reproduce the symptoms very well lately. ill keep putting the AC to 4 and see if i can get any more info on the behavior, i wish we could post videos clips on here, it would really make it easier sometimes.
 
Just post the youtube link.

You may have a small vacuum leak, in a vacuum hose that is confusing the O2 sensor..., one that is actively leaking when you turn on the AC. Did you ever check the vacuum lines at the passenger side firewall area. get a map of their routing and check them all. Even a tiny leak can cause issues.


i know it might have been far fetched, but i couldnt have hurt to asking while im digging for answers.

with the mileage it has i could see the IAC maybe, but i havent been able to reproduce the symptoms very well lately. ill keep putting the AC to 4 and see if i can get any more info on the behavior, i wish we could post videos clips on here, it would really make it easier sometimes.
 
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