Gs400 Idle Problem

98gs400 · June 20, 2003

Hey guys I have a 98 gs400 with 47k miles, here's the problem. I started noticing this not too long ago. At a dead stop with the car in drive, it will idle at about 450rpms. But sometimes it would idle at 600-700 which I believe is suppose to be the norm.

If I have my a/c on then it does go up to about 700 or if i have it in neutral or park, it'll go up that high as well which is all normal. I took to the dealership, and they said something about my throttle body being dirty so they tried to clean it out.

After that didn't work, they ordered me a new throttle body and it still does the same. When I took it back after the install, they kept the car for a couple of days and then called me and said that it's normal and I don't have anything to worry about.

I took their word for it and drove the car home. It hasn't caused any problems or anything but I would just like to know why the heck it idles so low at times. I've tried fuel injector treatments and everything but to no avail.

I came across a guy at a import shop who works on Lexus's and he has the same problem with his gs400. He took it to the dealership as well and they told him the same thing. The problem isn't really hurting anything, but it would just be nice to know what it is. Hope someone can help out, thanks.

tedsmith · July 16, 2003

I have a Gs400 also that has the same idle scenario. When a/c off it idles around 450, but all other times it's around 700. I lexus dealer look at it and they hooked it up and said everything was normal. It almost seems like it might stall at low idle. Never has and I haven't worried about it since.

SKperformance · July 17, 2003

there has been a problem with the throttle bodies

and there should be a bulletin for a new revised one

and no it is not normal

it is what they ( dealers) told most customers as they were out of ideas to try

since toyota doesn't engineer bad parts normally

just needs to have a more open throttle

a good throttle porting would help

which is to remove a thin layer of material around it to smooth out the intake air

try the dealer again for a resolution

jzz30 · July 17, 2003

well if the engine doesnt die out and if theres no extra vibration you can feel than whats the problem it uses less gas right?

eddiek · July 28, 2014

I am having the same problem with my 2000 gs400. took it to an auto mechanic, he ran the scanner and a code came up indicating the Idle Air Control Valve looks to be the problem. also replacing throttle body could help. both cost about $250 from Rock auto.