hi guys lately when i use my a/c if i'm driving then cruise and put into neutral, the idle will stick above 1000 rpms and will sometimes VERY slowly try to climb down. have only noticed this with a/c and is not constant but enough to cause to ask. any ideas/solutions?

 

Ac is hooked up to belt and needs to be spun at a certain speed for your AC to work correctly. This is why its really only recomended if you are driving since your belts would be going fast anyways.

 

^ yup... your idle depends on engine load. If you turn your a/c on, it'll idle high. a/c off with the fan on, and it'll idle around where it's supposed to (if the engine is warm); I believe it's somewhere in the neighborhood of 800rpm. Turn the a/c and fan completely off, and watch the idle drop down to 500 or so rpm.

A high idle with a/c on is perfectly normal, and nothing to be worried about. Just remember that a/c on a small engine draws from the engine's power quite a bit. I'd recommend turning off your a/c when you need to accelerate or go up hills. If you're just cruising on the highway, by all meanskeep the a/c on. Personally, I almost never use my a/c (only to defrost/de-fog quickly), and as far as I'm concerned, the fan is used for one thing: keeping air moving around the engine bay at stop lights (aftermarket headers create a lot of heat). If it's nice outside, my windows are down and the a/c's off

 

Well, yeah. But the A/C should be able to function even at idle... albeit not as well as with the rpms up a little higher.

The thing that's causing the idle to rise and fall when the A/C compressor engages/disengages is the Idle Air Controller. The IAC takes its cues from the ECU. After receiving a signal that the A/C compressor is coming on, the ECU tells the IAC to open up a little, letting more air in and causing the injector system to compensate for the extra air by injecting a little more gas. Tons of computer stuff going on for even the simple little things.

Bottom line - this is a normal function. Don't worry about it until it doesn't happen anymore.

 

Yeah I use to wonder about this myself until I realized that the AC is running off of the belts so yeah its gonna cause a higher idle than if the AC was off. You have nothing to worry about.

 

You can get away with that in PA.

West Texas.... not so much.

 

Lol yeah, when i visited there 100 and over degrees everyday is not so much fun. You NEED the a/c on all the time

 

thanks guys i totally understand the idle should be higher than normal, my problem is (this is happened 3 times since using a/c this week) if i'm gradually accelerating and i decide to slow down or come to a stop, put it in neutral, let foot off gas. the idle will stick above 1000 rpms maybe like 1500/1800 rpms as if my foot is still on pedal. i drive off then its fine at idle next time. again only with a/c on. otherwise the idle with a/c on is about 800/900 rpms which i know is perfectly acceptable.

 

That's a nifty feature of the IAC. It gradually steps down the exhaust, instead of returning back to idle ASAP. There's a bunch of reasons why it does that, but the one that cracks me up the most is 'it helps you to not stall out on a hill.'
I wouldn't worry about it.