Almost stalling when A/C on

[takumidrift30]

Prior to it she's running perfectly, idles at 700 rpm even when a/c on.
Now idles at 700 rpm once a/c is on turned goes down to 500 rpm and stopping from momentum sometimes stalls.
Checked all vacuum, and hoses everything ok. What could it be?

[BennyM]

Does the idle fluctuate at all or just drop with AC on? It could be a failing or dirty idle control valve.

My other guess is that the AC compressor is about seized. Not sure how to test that though....

[takumidrift30]

Does the idle fluctuate at all or just drop with AC on? It could be a failing or dirty idle control valve.

My other guess is that the AC compressor is about seized. Not sure how to test that though....

The idle just drops down and steady at 500 rpm. The compressor I just changed it with a reman 6 months ago.

[BennyM]

I'm going to assume that the reman is still OK. So, I know it's a pretty straightforward setup, but is there any chance the belt has too much tension?

I'd definitely take a look at the ICV if I were you. At the very least, measure the resistance and voltage values at the connector to make sure that that part of the system isn't electrically faulty. And cleaning it, if you haven't will only help your engine.

The idle just drops down and steady at 500 rpm. The compressor I just changed it with a reman 6 months ago.

[genphreak]

The belts automatically tension, so so long as you get the size correct they'll be okay. Won't slow the engine down anyhow (they'd break doing that). Most likely the ICV, pull it out clean it carefully and make sure it works smoothly. Don't soak it with carby clenaer, just physicailly remove the oil with kerosene and a rag and a pinky finger... get it working smoothly, re-fit and you're back in the race...

Other causes- spark plugs, old boots/coil packs. Manifold gasket... **** But, is the fuel good high-octane (95+ RON) fuel? ****

[whiskychaser]

Shouldnt idle increase a bit when you switch on a/c? (The ZF atf filling procedure relies on it) A bit off the wall but are voltages with motor running what you would expect?

[632 Regal]

have to agree the ICV is most likely sticking not allowing the engine more air when the AC is switched on. The ICV is supposed to keep the idle at the same rpm regardless what is on so if it's dropping then I would guess thats the culprit.

[takumidrift30]

have to agree the ICV is most likely sticking not allowing the engine more air when the AC is switched on. The ICV is supposed to keep the idle at the same rpm regardless what is on so if it's dropping then I would guess thats the culprit.

That's good to know, my perception of gauging faulty ICV is only when the idle is erratic.

[Kibokojoe]

Is this a drive by wire? If not I concur its the ICV

[genphreak]

I think it depends if the engine is warm or not. At temp I notice no differnce. It probably generates less torque at idle when in warmup, so they might increase idle in this case, ever so slightly, when AC goes on to sort-of compensate... only guessing on that