I'm posting this same response in a few threads for this problem in the hope that someone else will benefit from it.

My idle problem is fixed, and by that, i mean the problem where it does not remember the correct low idle after turning the car off.

I did a couple of things differently during my last reset, which i'll explain below, but here's the points i used.

1) Car fully up to running temperature (required)

2) Reset performed per the book, correctly takes new idle setting (as normal each time i do it)

Two things i did/did not do this time that seemed to make the difference:

1) I turned off the interior fan before starting the procedure.

2) I did not rev the car a few times after the new lower idle had taken (even though the procedure calls for it)



I have no idea which of those two made the difference. All i know is, that it's now remembering the new idle and it's super smooth.

I had loaded a new map on the car a week previously, and i had the door open and the fans on low with the engine off for a few mins before starting it, i do have LED interior bulbs.
However, it complained of battery voltage too low and would not let me flash until i had closed the door and turned the fans off.

This has never been a problem before when flashing and whilst i don't think it's a problem directly, i'm wondering if it showed up another problem that perhaps contributed towards the issue.

The battery isn't that old but it's possible it's not as well as i thought, I'm thinking the battery voltage during the reset procedure, which is done with the ignition on but engine off, was causing a problem with the learning portion.


Short version;

* I came home and turned off the engine, fans and kept door closed.
* I ran the procedure, acquiring the lower idle, but omitting the rev testing at the end.
* Turned off the engine and shut the car up for the night.
* Everything perfect once up to running temperature the next day.


Hope this helps someone out.

 

having problems this problem my self after i change cam n crank sensors guess im goind to give this a try and do the who thing over before i take it in im seriously annoyed!! thank good i have another car to drive in the mean while
MPG's BABY!!! Prius FTW hahaha!

oh and i guess im going to try and clean the sensor and MAF as well

this was a lil useful thanks guys

 

Well, I've been having this issue for about 3 weeks now. Cleaned TB with 3M kit. Didn't even touch them, just sprayed the cleaner on them after doing the drip injection into the air duct.
Idle was around 1500 after I put everything back together. Idle relearn returned it to normal. However, it wouldn't stick after restart. It didn't go back to 1500RPM, however, but 800 just like the OP. Annoying rev hang, too.
I have an amp and a sub in the back that aren't listening to the power-on cable like they should. I can hear the capacitor squeal when I turn the car on, even if the head unit is off. All of the idle relearns I've done (more than 20), I've done with the amp plugged in. Everything else was off though (fan, lights, all of the 12V devices, even unplugged the UltraGuage). I will try to do the relearn after unplugging the amp tomorrow night. I know the requirement is over 13V on the battery, which doesn't give you much room.
Keeping fingers crossed.

 

Update.
Disconnecting everything possible and doing the re-learn did not help. It would still forget it on next start.
Disconnecting the battery overnight fixed the problem. First start after reconnecting the battery showed the right idle and normal RPM drops. 4 trips since then and it's holding the settings. I did not have to do the re-learn after drain.

 

Sounds like it gave the battery a good chance to recover with no load overnight.

Great news though, glad it's fixed

 

Should I disconnect the neg and positive terminal? Or just neg cause I have this problem as well after clea ing the tb and now after relearn process is taken place it idles smooth at 650 until I shut the car off and it's back to 900-1100 rpm.

 

You shouldn't need to disconnect the battery at all, read my posts in here, but if you still want to, just the negative is fine.

 

I am just having some issues myself. SEL came on a couple days ago and notice that the car's idling had jumped from 650 to 1100rpm. Car idles fine when i first start it up for a warm up (around 650rpm). But when driving for about 30mins (commuting to work) car is now idling around 1100rpm. It also feels very sluggish off the line. I notice that this happens when the car is fully warmed up and driven for an extended amount of time.
I have about 85K miles and have not cleaned the TB and MAF yet. Could this be the issue? The Z has not have any issues with SEL and high idling until now. I have a smog check coming up and would love to have fixed before that due date. Any insight would greatly be appreciated. Thanks in advance!