fortitude

For the first startup in the morning, the engine begins with 1200 rpm, after 2 seconds, it rises to 1600 rpm, after 2 seconds it goes to 1200, then 2 seconds to 1600 then settles at 1200 rpm.
This only occurs during first start up in morning. It does not last through-out the engine warm-up cycle.
I live in Southern California so it usually does not go below 60 F during the day but can drop to 45 F overnight.
While the engine is warming up the idle does not continue the "searching" and slowly reduces itself to 500/600 rpm once warmed up.

MAF - cleaned
Throttle body butterfy - clean
Air filter - clean
Plugs - fairly new
NO CEL

808mcv20l

Do you turn on the AC as soon as you start up the car?

Being in CA, there's a good chance that you do.

Us in Hawaii turn on the AC right after we start up the car.

I saw that you cleaned a bunch of stuff, but I would check the IACV (idle air control valve) which is notorious for getting gunked up.

It's a real pain in the *** to do a proper cleaning on it though. I removed the entire throttle body and removed the philips screws holding it on. (make sure you get a good grippy screwdriver or use a Rachet with philips screw socket, you don't want to strip those screws.

once you have it removed, clean out the entire IACV with carb cleaner. i put a little bit of di-electric grease on the rubber gasket afterwards to prevent leaks.

fortitude

No A/C on start up.
Is the large black plastic unit on the right of the throttle body the IACV? It has 6 screws holding it in. These philips screws have almost a flat head. I will remove throttle body from vehicle first Then was thinking of helping them along with light pressure of vise grip plus screwdriver but looks too tight.

crwys

For the past year my 99 es300 had some fluctuations with rpms from time to time, especially with turning on the a.c.. My fuel pump just failed about a week ago. So it may be a sign of your fuel pump failing. I could be completely wrong though.

808mcv20l

Ohh that looks like a fly by wire throttle body.

In that case there is no IACV, I had a similar problem on a 2010 Honda CRV, hunting idle and dropping idle. I was told to never operate the butterfly with the power engaged as it could take a finger off if it closes automatically.

What I did was remove the entire throttle body and cleaned it out completely with carb cleaner, just be careful around plastic parts as it can melt it.

Another place to look at is the EGR valve which can get clogged and the MAF sensor that needs cleaning.

It's also a good idea to check around for cracked or broken hoses that can lead to a vacuum leak. you can spray around the hoses with the engine on with a combustible fluid, what that will do is if there is a leak, it will be sucked in and you will hear the engine rpm rise momentarily.

Oro

Given the prior info, this is where I'd start.

Look particularly around the rat's nest forward of the air intake over the battery. This gets dried/cracked and is a real mess that I think does not get put back correctly when batteries are changed and air boxes pulled. Many opportunities for error. Part of it runs down to the front motor mount and its total Rube Goldberg mechanism, but if not solid overall results in idle abnormalities.

If other things seem normal, and someone besides you has ever changed the battery or for any other reason removed the air box, check this as it likely will not have been re-installed correctly.

I do not disregard crwys' point. But I would rule out engine air and vacuum abnormalities first before going into other systems for a source. Fuel pumps and pressure regulation systems on post mid-90s vehicles are very good, the bad lessons were learned in the 70s and 80s. So I'd suspect it later down the diagnostic tree, but is a valid consideration.