A/c causing my throttle to fluctuate and drop too low

[timallen]

Hi! Newbie here.
I am having a problem where my throttle at idle starts fluctuating from a straight 500 rpms to 700 down to 200 or so and rattling. If I turn off the A/C, the fluctuation tends to slow and moderate back to 500 rpms. I have replaced the throttle body and had the computer reprogrammed but it has started again . I do not know what to look for next. I have watched several videos and the problem seems to a recurring issue but seem to be corrected with either the throttle body replacement or the programming redone but nothing I have seen for the next step if that does not correct the issue?

 

[Doubeleive]

Hi! Newbie here.
I am having a problem where my throttle at idle starts fluctuating from a straight 500 rpms to 700 down to 200 or so and rattling. If I turn off the A/C, the fluctuation tends to slow and moderate back to 500 rpms. I have replaced the throttle body and had the computer reprogrammed but it has started again . I do not know what to look for next. I have watched several videos and the problem seems to a recurring issue but seem to be corrected with either the throttle body replacement or the programming redone but nothing I have seen for the next step if that does not correct the issue?

some fluctuation is going to be normal when the ac pump engages/disengages.
when was the last tune-up?
how many miles on the spark plugs/wires
do you ever use injector cleaner or have had a injection service done?
how old is the air filter.
some people have had a tuner increase the idle speed a tiny bit like 600-650rpm
unless your ac pump is taking a dump then it's basically going to be general maintenance to get the idle more stable.

 

[Fless]

Moved you here from the General Discussion section.

 

[LsHart]

When the compressor kicks in the idle goes up to compansate. Will never go away. Rpms have to go up to deal with the compressor engagement.

 

[Doubeleive]

When the compressor kicks in the idle goes up to compansate. Will never go away. Rpms have to go up to deal with the compressor engagement.

going up is not the problem

 

[LsHart]

That's what fluctuate is. The going up and down. Also called hunting. Compressor kicks off, then the idle returns to normal. Am I missing something?

 

[Doubeleive]

That's what fluctuate is. The going up and down. Also called hunting. Compressor kicks off, then the idle returns to normal. Am I missing something?

yes his idle is dropping (too much), he stated as such in the initial post, 200rpm is bad mojo. most likely needs maintenance, plugs, wires, air filter, injection service, clean the throttle body and maf. he also needs to check what is rattling, it could be a heat shield, it could be the ac pump is on the way to heaven they can make some wicked noises when they take a dump, it could just simply be the very low idle and engine internals when it idles too low (engine knock)
other things to check would be fuel pressure and the fuel tank vacuum valve on the drivers side of engine, ambient temp sensor, map sensor

 

[LsHart]

Sorry, but was just addressing the forum title. I might have missed something. All is well.

 

[Marky Dissod]

some people have had a tuner increase the idle speed a tiny bit like 600-650rpm

Some people go so far as to ask their tuner to raise the AC idles even further.
My P/N AC ON idle is set @ 800RpM (same as any GM OE V8 with a stick shift).
My R/D AC ON idle is set @ 700RpM (same as any GM OE PPV with a 4L60E).
My AC OFF idles are set lower.