rbcomp

Hi everyone

I know there are a bunch of threads that discuss this issue but it seems there are a few different causes and solutions. Is there a definite guide out there to help troubleshoot? I'll describe my issue below.

Sometimes, not all the time, when stopped in drive the car idles at ~500rpm instead of the normal ~750rpm which causes for a rough idle. It seems to occur when it is a bit cold outside, but I'm not 100% certain of this. A while ago, I found that when I would turn on the AC, the idle would go back to normal. This does not seem to work anymore. I also note that when I put the car into Neutral, it goes to normal RPM as well.

I tried cleaning the MAF sensors this weekend. Thought that helped as the problem did not occur for 2 days in the cold, but alas the issue returned this morning.

I believe the next step is the clean the throttle body, but before doing that I wanted to post and see what others have found. Maybe I'll create a definite guide if one is not out there already.

* Car is a 2011 LS 460 AWD

Thanks

Vtallysx4

2013 AWD- With the A/C off my car idles real low too, since I've gotten it. Car has to be completely warmed up for this to occur. If it is not up to temp it will not do this.

roshko

Since replacing my spark plugs and cleaning the throttle body I have not had my car experience a low idle since.

rbcomp

Hrm, spark plugs is a new one. Did you do both them and the cleaning throttle body at the same time?

Striker223

Probably buildup in the throttle body, or plugs if it's high mileage. These cars don't have a separate IAC valve/motor so everything is done based on the TB, clean it and do a relearn with the engine hot

Anfanger

If you are going to clean the throttle body, be careful around the butterfly valve. You want to avoid rotating it by hand it as much as possible.

fwhomeboy

I'm curious about the T/B relearn procedure. I guess I'd better start a Google search. Thanks.

Striker223

Yeah, put a brick or something on the pedal to move it around not by hand.

3GSShoe

I keep thinking my car would stall out. I’ve had 3 LS’s and they all do this. There’s no rhyme or reason why or when this occurs. Symptoms are the same- when the car is warmed up, sometimes with AC on or AC off, the idle drops to 600-650RPM

With AC off, this usually drops to 500-600RPM.

Someone else who brought this to Lexus has been told this is normal. My Lexus mechanics don’t know why the car does this either.

Gerf

I have no idea whether this has anything to do with the low idle or not but it's what I've noticed...

My car was doing this for the first year I had it, wasn't running rough but the rpm's would get low at times only when the engine was fully warmed up.
Early this spring I tried Amsoil and later Royal purple, I was trying out different brands since I got the car and started with Mobil1 then Pennsoil ultra...anyway I didn't think there was anything noticeable in the way it ran/engine noise etc but I've realized that since using Amsoil and RP my car hasn't dropped the rpms once in 7 months.

Like I said, no idea whether that contributed to the condition or not, just an observation. I've done 6 oil changes in 2 yrs with this experiment so maybe it was an unintentional flush of the VVT system or it might just be my imagination lol.

2007ls460l

2007 ls460 w 220k miles
have had this issue since car was purchased used
recently cleaned both maf sensors (w maf cleaner, ensured all carbon was cleaned off) and replaced (very dirty) air filters, issue resolved
ymmv

Gerf

There are a few of these threads on this site and it seems like everybody is susceptible to their own preferred placebo, it's probably just a glitch in the software for the target idle speed.

napamikey

My 2012 at 270k miles was idling low after a service. Pressed the 'auto' button on HVAC and all good. It sucks but is a 10+ year old car approaching 300k miles.

THE_CEO

Have you checked your engine mounts? mine idle used to do the same thing until i got them replaced.

Vtallysx4

Mine idled low in drive and you felt it in perfect weather with a/c off. I replaced the motor mounts, it will still idle low in perfect conditions with Absolutely no load on the engine, but, now I don't feel it.