Their is no Lexus category so im posting this under Toyota. about 2 weeks ago i purchased a 1993 Lexus sc400. I am having a problem with the idle. when i first start it up when it is cold, it will idle between 1100 and 1300 rpm, but as soon as the needle comes up on the temp gauge, it starts to rev up and down between 1100 and 2000 rpm. I have a lot of plans for this car but i don't want to start putting money into it until i figure out the problem. I've been told told many things, but the main thing i have been told is its the idle air control valve so last night i took it apart and it turns out the bearings on it were all sticking so i cleaned em and loosened them up but it didn't help at all. Please Please help me!

 

just replace the iacv pretty sure thats your prob. cleaning them doesn't always fix the problem.

 

I would just jump to that conclusion but thats a $900 + fix for a brand new one. I would like to start with something a little cheaper. Is their any way i could test the iacv before i go and spend that kind of money?

 

Clean out the entire throttle body. The carbon buildup that accumulates in the IAC trac can be part of the problem. Also make sure there are no loose or cracked vacuum lines. Lastly make sure the TPS sensor is properly set. These are all things that can screw with your idle.

PS: Never buy stuff from a dealer unless you absolutely have to. IAC valve can be have for $50 or less on Clublexus/Ebay/etc.

 

Thanks alot! im gonna try all those tomorrow. HAh its gonna be fun going over all the vacuum lines!

 

You can find one on ebay or in the junkyards if the cleaning does not work for you. How many miles are on the car just wondering? Is it when you are sitting at a stop light after running for over 20 minutes? Or is it just after like 5 minutes? I could help you out if you need it.

 

Thanks alot for the help, When i first cold start it, it idles at about 1100 - 1200 rpm, but as soon as the temp needle comes off the peg on the dash cluster, it starts to rev up and come back down, between 1200 and 2000 rpm, This makes it very difficult to drive due to when you let of the gas it still acccelerates even at 60mph. Something i have noticed is it sounds like IACV is trying to correct a very high idle when it is doing it.

EDIT: and it has about 164000 miles on it.