Have you ever had the carbon build up rebuild performed on your engine?

 

 

This video will help explain it, as the IS250, and the 2006 GS300 both were recalled in 2012. You will start to see it over 100K miles! There are cars that will make it close to 300k miles.

There are other options now to clean your engine, you can remove the intake manifold and by hand with chemical spray them into the intake ports and scrape off the carbon, you can use a stiff tooth brush. Seafoam through your intake manifold, heat the engine and from the intake port, attach a small vacuum hose and pour regular seafoam in a cup. With your engine running let the vacuum from the hose slowly suck in the seafoam, pause every 15min and keep repeating until you pour in atleast a bottle and half. This also another option but it will not get the majority out like removing the intake to access the valves easier. Once again this is only if you have carbon issues.

 

Don’t have carbon build up and the car has 70k on it . I think the idle needs to be relearned

 

How did you check for vacuum leaks. Did you use a smoke machine there is normally a hairline crack in the rubber hose that goes to hard line running down the right shock tower, which goes to the evap purge but this would sometimes set a evap purge/ leak fault.
Did you clean the Maf sensor also. Try disconnecting the battery for a while, reconnect turn key to on without starting leave like that for a minute and then start the car. Let idle for 5 minutes then take it on a drive see if that helps to relearn the throttle. If not you may have to get the techstream and force a relearn with the computer.

 

 

Yes press button once without stepping on the brakes this will put you in key position 2 the throttle motor will do a quick self check. After a short time you can start the engine (press brake and then push button again).

 

You should check out this video for reference on troubleshooting.

GL!

 

Nice video Goku. Unfortunately 2006 gs300 have no separate idle air control valve and uses the main throttle body to control idle based on several input sensors such as ambient air temp, coolant temp sensors etc. I've seen issue of this problem before here and some have had to replace the throttle assy. itself.
To properly diagnose a would read fuel trim. smoke the intake system (maf sensor back), can also spray around intake manifold with brake clean with engine running and see if idle changes, remove throttle harness check wiring doesn't get pushed back when reinserting check corrosion on terminals, double check nothing is hanging the throttle blade open ( remove intake boot, have some one cycle key while you look at the throttle valve.

 

Thank you for clarifying! I wasn't sure if that video would have applied to our vehicles or not. I try my best to help as best I can on my spare time

 

Spraying starter fluid or carb cleaner around the engine is a good idea to find any air leaks that may increase the idle. But the best way is to try and diagnose it with a good scan tool and read the fuel trims and see what exactly is increasing the rpms.

I still believe it has to do with carbon buildup, Ive had the same issues when I had an is250 and that had higher idle.

 

Did you ever find out the problem with your car? Mine is the exact car doing the exact same thing. Throttle body and MAF sensor have been replaced and i still get the P0505 code.