Taiwanese

I have been lurking here for many years.

Recently, I have been driving a family member's 95 LS400 (to keep battery charged). 1995 with 64k miles, mostly city street driving.

I noticed the idle is about 1800 rpm when the engine is cold (in the morning or in the afternoon after sitting the entire day). I let it warm up for couple minutes and the rpm is about the same. As I started driving away, it feels like the car is running away (due to high rpm). The rpm will be about 800 after a few more minutes of driving.

Is this normal? It feels like back to the old choke / carburetor era. Isn't this fuel injectioned engine?

Lex-Fiend

I had the same problem this past sunday. I let the car warm up comletely before driving off it was fine. Its been fairly warm since then so it hasn't happened again.

Sixdown

I get a similar problem, in cold weather, as far as I've noticed. The RPM when I first start the car hover upwards very slowely from 800 to 1,600, and stops there until I put the car in reverse or drive. I haven't had the car in warmer weather so I can't tell you if it happens in warmer weather.

Any ideas? Is it the thermostat?

4TehNguyen

iTrader: (1)

tons of cars do this, it isnt a problem, rpms are raised so the oil starts recirculating faster and the oil and engine block warm up faster during cold weather starts. My prelude does this, my IS does this, same with my moms avalon and LX

Taiwanese

4TehNguyen,

I know most cars' idle will be higher (1000 rpm?) when engine is cold. But not at 1800 rpm. And it feels like the car is running away (I have to step on the brake hard).

dfkd

This is completely normal.
From what I've read, the purpose of this in every car is to heat up the catalytic converter as quickly as possible because they work most efficiently (to do their job of reacting out the unstable oxides in the exhaust gases) when their temperature is up at a certain level (above 500 degrees).

sonyman

You guys that are calling this normal are missing the point entirely. Yes, fast idle is normal. No, an 1800 RPM fast idle is not normal.

richonenz

An 1800 RPM idle IS NOT NORMAL !!
I would check out the ECU temp sensor first and also do the one for the temp gauge at the same time .
I have heard of a lot of people with this problem [ including a couple I know well ] and they have gone through and changed/replaced/adjusted nearly everything that could have an influence on the idle with no result .
What people forget to consider is that the reason for the fast idle in a lot of cases is that THE ECU IS TELLING IT TO IDLE FAST !!
So if you track back with that in mind then either the ECU is faulty [ not the most likely thing ] or it's getting faulty info = ECU temp sensor , so replace it , it's probably overdue for replacement anyway and they don't cost much .

Zoraone

I've had a lot of cars with varying idle speeds when cold.

The worst was a 1989 Honda Accord. It would have an initial idle speed around 2,500RPM in sub zero weather.

Even my 2003 V6 Accord would idle around 1,500 RPM when dead cold.

My families LT1 cars will idle around 1,200 to 1,400 when cold.

The LSx cars in our family idle about the same when cold.

I have yet to start the LS400 today. It is pretty cold here in Indy so I'll see where it idles.

Taiwanese

Maybe I should be more clearly on my first post, 1800 rpm when engine is started regardless of what the outside temperature is. It will drop down to 1200 rpm when put into reverse or drive (feels like car is running away and had to apply brake harder).

Sixdown

Basically the same thing I repeated on the second post. I have the same problem when going into D or R. The idle cruise speed it way higher than any of my other cars.

LS400_Fan

sorry for being late to the party on this one (i was searching brakes and looked in) but while driving around many LS400s before i bought my own, i found that all LS400s have a high cold start idle that is around 1600-1800rpms that will drop a few hundred rpms within 90 seconds or so to about 1200-1400 and eventually as it warms up enough gets down to its normal idle.

LS400s have a high cold start idle, much higher than any other car i have driven/owned/used.

RexFender

My LS400 has the same 1800 RPM idle, it never really bothered me until I had a rather embarrasing moment a couple of weeks ago..
I overslept a few minutes and was in a bit of a rush to get to work. I jump in the car and hit the garage door opener. So far so good... As I back out into the driveway I notice a thin layer of ice coating everything in sight, not just any ice, but that rare super slick stuff that makes it an adventure just to stand. I gently touch my brakes and turn the wheel to line myself up in the street, here's where it gets funny (only because I didn't hit anything) Since the engine is roaring away the only wheels that stop turning are the front, resulting in no change of direction but my first instinct on ice is not to jam on the brakes. So I continued backwards in a straight line right across the street into my neighbors driveway! (good thing his lines up with mine...) Ok, that was fun, now I shift into drive and turn the wheels the other way, again to line myself up with the road and head slowly off to work. But nothing doing, still into the powerband at 1800 rpm there is no happy medium where I can slow down the back wheels to prevent careening off into the ditch and being able to let the front wheels roll a bit to change the direction of the car... Straight back across the road I go..
I end up back in my own driveway, now danger close to my wifes car. This comedy of errors repeated itself five times... I finally got the snorting beast back into the garage in one piece with only my pride injured. Yes, I made it to work that day, I woke up my trusty 1990 Ford F150 2wd manual trans with 365,000 miles on it and never had a problem...
While an 1800rpm idle might be "normal" there are times when it is down right dangerous. Mine takes almost 20 minutes of driving to idle down a bit. Yes I will be checking out the temp sender..
Take Care All

Bill Dowd

I have the problem of 1500 rpm here in Southern California and I use mobil one 5w-30 extended which will also let the engine run at a high idle for about 5-7 minutes. I just let it sit there and run till it feels it want to drop to 600rpms. Some people say it's bad to let an engine ldle but I have been doing it for 10 years now and no problems at 197,000 miles. The only thing that has gone wrong in my 91 lexus is the power antenna I still have the orginal hoses air cond power steering unit. changed out the seals on the ps unit I use mobil one synthetic oil in everything. One thing I did was to add a K&N air filter and picked up 1-3mpg on the open road now getting up to 25mpg if I don't stick the pedal to the medal.

Neofate

iTrader: (1)

On topic: It seems this is common, but still doesn't mean it is in 'proper intended function' Or in other words maybe alot of these older Lexus's simply have yet another common problem. Though a high idle is not damaging the engine, if anything it is helping everything get lubricated on a cold day. -- Not top priority,.. now in ice as was mentioned.. I can see the annoyance. Luckily down south I don't have to deal with that but once every few years.

To the quote:

I've heard the opposite. I have heard that it is best to let the engine idle for a minute when you first start it after it has set for the night/a day, or longer. So the engine becomes lubricated and warms up before putting any major stress on it. Why would it be bad to allow an engine to idle?