the check engine light can come on if the gas cap is not tight enough
and it goes away once restarted with it tight

also after 3 cycles of the key the ecu should turn off the light if their has been no code since

 

lexus service looked at my car, and found nothing. code wasn't able to provide anything. even with
no check engine light, the car seems more hesitant from complete stop to acceleration. they may
change the fuel pump, as long as warranty covers it. i'll find out for sure on monday.

 

I've had Lexus of Portland (Oregon) try to cure my low-idle issue three times thus far. The first two times, the low idle was evasive enough that it didn't do it while the car was in the shop.

A few weeks ago, with the warmer weather--which seems to cause the problem, I let them take another crack at it. This time they decided to clean out the carbon build-up in the throttle body--which isn't covered under warranty, but they were nice enough to do gratis. This change seemed to reduce the roughness by about 50%, but it was still idling below normal speed.

The next day, on the way home from work, I was slowing down to turn off of a highway (thankfully) when I felt a lurch, and the "Check Engine" and VSC warning lights on the dashboard popped on. The engine was idling around 1500 in Drive, and when I tried to press on the gas pedal, there was no response. I limped into a parking space in the parking lot I was turning into, and called Lexus of Portland.

To make a long story short, my GS400 was towed (how embarrassing!) into LofP and they diagnosed it as a throttle actuator motor failure. There is a backup throttle cable, but my understanding is that it doesn't engage unless the accelerator pedal is depressed much further than normal--not something I wanted to try while maneuvering around a parking lot.

They ended up having to replace the entire throttle body, as the throttle actuator motor was not available as a separate item.

I would like to comment that Lexus of Portland made the very best of a bad situation. Everyone from the service advisor down to the fellow who shuttles cars around the parking lot expressed his/her apology for what happened. I was given an '03 ES' to use while my car was out-of-service.

With the new throttle body, the idle is still lower than normal. So couple this data point with the original poster who commented that he had his throttle body and MAS replaced and it corrected the low-idle issue and it looks like it may be the MAS that's causing us grief.

(Toy description: Cinnabar red '99 GS400 with rear spoiler, Nak' package, and 17" factory rims)

 

i cleaned out my MAF sensor and same story, still rough.

 

What's the idle you guys are getting when the car is fully warmed up? Let me rephrase that.....while you are at a complete stop in DRIVE. What's the idle? Is it between the 2nd & the 3rd line?

Is this with everything off? Well, except the daytime running lights right?

I've test drove several GS4s and most of them idle between the 2nd and 3rd mark and felt fine to me. Only one was slightly rougher than the rest.....hmmmm

 

How much did you paid?

 

^just so you know..this thread is over 6 years old

 

LOL...paid???