Odd idle issues

So the past few mornings I've had some interesting idle quirks with my 2004. I have two tunes that came with the car, a hot and a cold, and as the temperature has been falling, I tried the cold tune out this morning to see if that would change things and it does not appear to have made any difference. The issue I'm having is more or less a high idle hang and then a funny surge after it. I'll start the car up first thing in the morning and it will idle fine, even the next few stop signs it seems like it knows what it wants, but after warming up just a bit, when I clutch in to come to a stop the idle will hang high around 1500 rpm, then slowly drop to around 800, then quickly surge up to 1200 or so briefly before dropping back down around 800. You can even tell when driving that it's holding the IAC open or something, because it will still pull some with my foot entirely off the gas before it kicks into "idle" mode and tries to slow it down.

This would normally make me thing the IAC was flaky, but it seems like the car is fine when it's warmer outside (probably 40-50+). My next thought was maybe it was losing the TPS calibration so it doesn't know where 0% is? I noticed when I had the tuner plugged in yesterday that the battery readout was only 11.8 or so, but it faithfully starts the car every morning with very little drama or cranking. Didn't know it maybe it was drooping far enough overnight to lose the TPS memory or if something else was going on. Anyone have some ideas of what all to check while I'm diagnosing? It drives fine aside from the idle issues.

Believe it or not, it takes more battery power to run the car correctly than it does to start the engine. Look at your battery issue first.

My car doesn't seem to like the cold either, idles high for the first mile or so then goes back to normal. Happens between shifts and at stops, seems to idle fine after it warms up. I have an '04 as well

I agree, spend the 120 bucks and swap out your battery for a new one. Then report back to us

It seemed to work itself out finally, but I think I still might get a battery this winter before it's all over. I tried the TPS relearn procedure and finally seemed to get something to click on it and it's been okay. It did sit for my 4 day holiday weekend though, so I'm curious to see what it does after sitting that long. I figure if it is a weak battery it'll show it after that. Wasn't too bad this morning, but it did seem like it hung the idle just a bit, so I'm guessing the battery is the most likely culprit. Need to see where I can get a good one in town.

So just to make sure I've found the correct info in my searches, what is the TPS relearn procedure? I've heard key on, zero to full throttle something like 3-5 times and that should be it, but I didn't know if you were supposed to turn the key off after or start the engine right after. Tried it this morning after a fresh battery and it doesn't seem to have done anything. Idle is gradually working its way back after the drive to work, but it's still kinda wacky.

Okay, might have found the reason behind the funny idle after learning some other issues. It looks like my power steering fitting finally wore out enough to leave a noticeable spot under the car. When I pulled the cap to siphon out the rest of the fluid before pulling the line, it was just barely on the stick. When I replaced everything and filled the reservoir back up, the car idled high initially until as it drew the new fluid into the system. Once I cycled everything a few times and topped it off the idle seems to settle faster now.

Long story short I think I might have been running low on power steering fluid and the reduced load on the system was making the car idle high. Leak fixed and fluid topped off and it hasn't done it again yet.

Good News!!!