Idling/RPM question

[Crackseed]

So I was reading a thread over in the TSB section re: idling and I did notice something recently - a few times while I'm just idling [this past Friday - left the car on for about 15 mins while waiting to pick up the g/f from the airport] and I noticed a couple of times the engine would drop from it's customary 700-600 range and dip just below 500 then come back up.

Is this anything to be concerned about? As I've never owned a car with this kind of engine, etc just want to make sure there's nothing worrisome about this behavior. It's not super common, just happens here and there when I'm idling [happened at a stoplight for example] and beyond that, no other issues; car isn't stalling, no strange noises or knocking and still no crickets.

So, should I be worried? >.>

[Sigh-on-Rice]

Mine does that too, but I'm not sure if it's same as yours. Mine idles at 600 rpm without A/C and it's always stable. When I turn on the A/C, sometimes it idles at 650 rpm and some other time idles at 700 rpm. And from there, it only dips somewhere between 0 and 30 rpm whenever the compressor turns on. Only about once a month, what you described happens when the A/C is on. Every time the compressor turns on, which is about every 15-20 seconds, the idling rpm drops to about 500, I feel a little bit of shake, and then jumps up to 800 or so. It would do this every 15-20 seconds until I turn off the A/C or turn the engine off once. When I start the car the next time, it doesn't do it anymore until a month or so later. It gets pretty annoying, but since it happens so rarely, I can't really do anything.

[wheelhaus]

I have a similar experience as Sigh. I also have rock solid idle at 600rpm when the AC is off. When the AC is on, it will dip and jump +/-100rpm right when when the compressor kicks on.

[Crackseed]

I think that is the same reason then since I always have the AC on. Good to know its not just me.