Low Idle

[difuria]

I have a 2002 ES300 with 115,000 miles on it.  It runs good, except for the occasional jerky transmission and constant low idle issue.   I realize the transmission is a flaw with the year and there's really nothing to do about it. 

I'm more concerned with the low idle.  I started to notice the low idle last year with the air conditioning on.  It idles at a round 450rpm.  When the air turns itself off the idle raises to about 600 but slowly lowers to about 500rpm.  The car runs a little rough around 450rpm, but smoother at 500rpm.  Normal rpm is 500 with the air off.

I've cleaned the throttle body numerous times.  The rpm is around 750 after a good cleaning, but over the course of the day drops to its standard 500rpm.  I've also reset the computer numerous times.  It idles at about 750rpm after, but again drops to 500rpm. 

Has anyone else had this issue?

Any suggestions on possible causes? 

[gbhrps]

difuria,

Factory maintenance suggests new  (iridium I believe) spark plugs at 100 000 miles. New plugs can make a whale of a difference.

Have you cleaned the IAC valve (idle control valve), tested it. If its carboned up you'll have the symptoms you describe. Maybe someone else will jump in with some other points to consider. Good Luck!

[difuria]

Thanks for your response.  I have not cleaned the IAC.  I have tried to locate it for the 02, but can't find a good picture or breakdown of it on the web.  I have an idea where its at, but i'd like to see photos of the inside and outside before tearing things apart.  Once I open it does it need a new gasket?  Does it have a gasket?  I assume I would clean it with something like carb cleaner to get the gunk off.

[gbhrps]

difuria,

Please realize that lots of things can cause idle problems, but one of the most common is a bad idle air control valve. I've included this YouTube video to help explain the issue to you. It's titled "

How an Idle Air Control Motor Works and Fails on a Lexus and Toyota

Two things to consider: you might be able to clean the IAC with a can of spray carburetor cleaner. The stuff is amazing at what it can remove and clean! It just might remove the gunk that's preventing the IAC from rotating. It sure makes sense to try it before buying a new IAC.

That said ... don't throw parts at a car trying to fix an issue ... if you don't know for certain that the part will fix the issue. You will just be wasting money if the fix doesn't work. Too manmy people have this approach and its foolish. My advice is to get a GOOD independent mechanic to diagnose the idle issue first. It may be the IAC, but it could be a bad coil, a bad injector, a dirty MAF sensor, and so on. It could even be a split vacuum hose. A GOOD mechanic can trace down the issue and save you money in the long run.

Finally, if you must try it yourself ... remove the IAC from the throttle body and try cleaning it to get that rotory valve to free up, and then reinstall it and give it a try. You just might get lucky. If that doesn't fix the problem .. see the mechanic before you spend any money fixing something that doesn't need fixing   ...  and still have the idle problem Good Luck and keep us posted on how you make out!

Gene

https://www.youtube.com/watch?v=L5M6ESEuVkk