My first check for idle issues is the throttle body.
Do you know if it's ever been cleaned before?

 

What is the temperature for your city during post #1 conditions?

I just put a new toyota OEM Iac valve on 96 camry 2.2 federal and when city is 20F and engine is started for first time in 24 hours : the rpm goes straight to 1750, 10 seconds later is 1250, 1 minute after that is 1500, it stays at 1500 for 1 minute, then it slowly starts decreasing (very slow gradually until it reaches 750, and I'm unsure how long this takes)

I am unsure if this is normal, but I have no codes and have not noticed any driveability problems.

I suggest putting a new one on and reporting back with results so we can compare.

 

Seems normal my 05 Camry acts the same. What were the RPMs doing before you noticed a problem?

 

Modern drive-by-wire throttles don't have IAC valves. They use stepper motors to make fine adjustments to the throttle plate angle at idle.

 

The outside temperature does not seem to make a difference. I live in NE just outside Philadelphia. It can be 20-50° and engine starts right up at 1800 rpm and 2-3 mins later drops to a reasonable 1100 or so rpm. Today it was 60 and while it went to 1800 as usual the rate seemed to drop a bit faster to 1100. I do NOT want to put car in gear at the high rate. I've never cleaned (sprayed) the "throttle body" although I did when I had an 1989 Camry. Not sure how that relates to the current issue.

 

Electronic throttle bodies have an idle learned value based on the operating conditions of the engine (such as how much air is entering the intake).
For example, if the throttle plate gets covered in carbon, the flow rate of air decreases, and the car starts to run overly rich. The ECU increases the throttle position until it hits the desired Air/Fuel ratio. It then commits this new value to its memory.
Your skepticism is not misplaced, as dirty throttle bodies usually have the opposite effect, causing too low of an idle and stalling, but it is possible that buildup is preventing the throttle plate from closing effectively. In my mind, cleaning a throttle body is free, and doesn't take much time. I also think it should be part of a maintenance routine, as it can affect performance.

The other thing I am thinking is it may be that the throttle learned values got reset. Did you recently have a dead battery, or disconnect the battery for a while?
That would cause all of the throttle position values to reset and possible give you weird idle speeds.

 

My '09 Camry acts similarly if the A/C is on when it's started, or if I turn on the A/C right after starting. I thought maybe it's a slowly deteriorating CCA in the battery.

 

I don't think that's an issue. The A/C compressor is putting extra load on the engine. The RPMs have to increase to provide the extra power. If the RPMs are really spiking, you may have excessive resistance in the A/C compressor.

 

"1100. I do NOT want to put car in gear at the high rate"
Try a snap throttle to bring rate down faster before putting in gear.
That said, been putting my 05 Camry in gear before engine idles down since it was new.
Haven't broke anything yet.

 

Around 122,000 miles I had the valve cover gasket replaced along with the spark plugs and a new $35 gas cap. I also had the exhaust system replaced ($$$$). The battery is 3 years old and hasn't been touched. I don't remember exactly when this "high initial idle" problem first surfaced, maybe around 125,000 miles (now at 127,000). The problem was after the work though. Once the car is 'warmed up' there is no issue, car will readily start and idle around 800 rpm. It's only when it starts after sitting for a few hours (days) will it initially idle at 1800.

 

Hmm... I wonder if you have a vacuum leak that seals itself up when the engine warms up? Do you have a scan tool that can read live data? If so, you can check the fuel trims for the car when the idle is high.

 

It's normal to start at a higher idle and slowly come down to 800-1000. Mine was irregular so i checked and cleaned the EGR and unstuck the valve (stuck open). Now, she runs better. Don't mess with the throttle cable if you have one. unless you are familiar with it. Mine was an easy fix compared to some. With the A/C, Check in-line filters, and ports ( L & H), belts, gas (maybe needs more), it could just be going bad. Good luck, Hope info helps

 

2007 Camry with 163k miles mine usually starts at 1300 rpm (no A/C or anything on) then moves down to 1000 rpm or lower within a minute or two. I thought this was always normal

 

Thanks all for the suggestions. I will play with a possible cure. It remains curious to me that on initial start for the day, the RPMs go to 1800 then after 2 mins or so drop to around 1100. Then, AFTER that start, for the rest of the day, the car will idle around the proper 800 RPM. My local Toyota dealer wants $150 to "diagnose" the problem and then whatever it may cost to fix it. No guarantee on the diagnosis.

 

Normal.About what my 04 does at start-up. Something as simple as lifting the battery ground strap for thirty seconds can set start-up idle back to factory set point. I replaced battery on my 04 V6 about two months ago and start-up RPM went from 1800 to 1600 RPM. ??