jasone36

Friends,

My low-mileage 2013 Lexus LS460L has developed a noticeable "violent shake" during cold startup.

It's especially noticeable when the car's been left outside on a chilly night.

Starting the engine on a cold morning feels like you're in a "tumble seat"... but within two-three seconds the car "calms down" and all is well... until the next cold morning engine start.

(My high-mileage 2002 Lexus SC430 had developed a similar issue when the SC430 was about 10 years old... I had the engine mount and transmission mount replaced, which solved the issue).

I'm wondering if anyone has any insight on this issue in the LS460.

Any responses would be appreciated.

Thank you!

superdenso

Are you describing rough idle, or a hard twisting motion like the engine is trying to turn the car over while starting-up?

jasone36

It's more of a "hard twisting motion like the engine is trying to turn the car over while starting-up".

Once it's running, the idle is smooth.

Rhambler

I think he's describing rough idle.

My brand new car had that and still does, although it's intermittent. I can feel the idling in the seats and attribute it to direct injection and fuel system while it builds PSI while trying to get the air/fuel mixture to the sweet spot, although I don't know for sure. My friends DI BMW is the same way and it might be just inherent of DI engines in general.

Startup fuel mapping is different I think due to emissions, coupled with DI, highly pressurized fuel rails and no amount of mounts will overcome this for the brief time it does this. I'm speculating but that's my best guess.

superdenso

It feels like the engine is trying to break loose from the motor mounts. It's the feeling of 300 plus horses waking up. In my opinion it's normal and I wouldn't spend one more minute worrying about it. It's a really good thing. My MB v8 will make the car dip

satiger

iTrader: (1)

Your car must be under 4 yr factory warranty unless its over 50k miles. Take it to the dealer and have them check that out. You may have to leave the car with them to reproduce this in a morning start. One of my engine mount was replaced under factory warranty, but I didn't feel shake during startups. Visual inspection by technician resulted such replacement.

enoch861

Sounds like an engine mount going out. In some cases it could also be a misfire during startup but this would be indicated by a flashing engine light.
My LS starts up nice and smooth no matter how cold it is with no noticeable violent shakes other than being able to hear it when it starts up due to the higher initial idle.

comotiger

If I recall correctly, you bought the car last winter, but never experienced this problem on cold starts. Violent shaking, however brief, is abnormal. I am inclined to suspect the engine mounts too (loose or worn). Have you opened the hood and watched the engine start up with someone else pushing the button? You may be able to spot the weak point. Hope you can get this problem fixed by your friendly Lexus dealership under warranty. Good luck and update us on the diagnosis and fix.

superdenso

Below are a few articles about engine twist; one fella provides the physics. My V8's twist upon start-up and that's with brand new dealer sourced&installed motor mounts and transmission mounts. Let us know how you make out if you choose to call or visit the workshop.

https://www.reddit.com/r/explainlikeimfive/comments/45pt89/eli5why_do_some_car_engines_move_a_little_to_the/?st=it6gtpme&sh=879ce24d
http://www.cruzetalk.com/forum/9-gen...e-startup.html
http://www.beamng.com/threads/car-le...ne-revs.13088/

Lynzoid

You can 'discuss' all you want - but this is motor mounts.
Replace them and you'll never ever feel anything resembling a 'vibration' - cold, hot, never.
I did. It's kinda hard, but the result will blow you away.

Stereorob

my 95 LS400 idles rough in the morning on cold start too. only for about a minute though. it smells like exaust and old gas for just a second then it always clears up and its fine literally 60 seconds later. pretty sure you are fine. ive always just chalked it up to "cranky old tired car that doesn't like to be woken up" but yours is only a couple of years old. also I have to start mine every 2 days atleast. if it sits for 3+ days its hard to start and runs like crap for a few mins. worst thing you can do to a high mile borderline classic lexus is to just let it sit.

after it warms up and collects itself, it runs smoother than the 460s. you could balance a coin on the 1UZ. the 460 is dead calm inside the car thanks to new technology but if you pop the hood the engine always vibrates a little. even the brand new ones. my theory is it has to do with the switch from timing belts to chains. youll never have to worry about a timing chain but the belts you gotta replace every hundred thousand miles or so, however they run much smoother.

roadfrog

Agree that this is indicative of a bad motor mount. Do you also feel any abnormalities when accelerating hard?

Stereorob

euro cars do this too. an audi A8, BMW 7 series, and merc S-class are all this way. on a cold start they run like absolute trash for a minute or so. even the brand new ones. probably due to the way the fuel injection system is set up. the 460 has also inherited this trait as well just not AS bad or long.

Lynzoid

ONLY if motor mounts are torn!!!!! No modern (esp. luxury) car shakes 'when cold' on it's own.
my car have less than 40k miles and my mounts were TORN! awd lwb. replaced all 5 mounts (3 rear, 2 front).

jasone36

Thanks for the all the insightful responses!

The shaking is not subtle at all, and is extremely noticeable upon start up... but no affects after that.

roadfrog, I do not notice any abnormalities when accelerating hard... although I try not to rev the engine too much, generally speaking

comotiger, I did buy the car pre-owned last winter but really didn't drive it much until the spring... and it was kept in a ventilated/heated parking garage... thus no true cold-weather. For all purposes, this upcoming winter is the first one for me with this LS.

Given my experience with the engine mounts on my ancient SC430, and the advice you guys have provided, I will definitely take this up with the dealer under the new-car warranty. Unfortunately, I won't get a chance to bring it in for a while (work constraints), but I will definitely update the thread when I learn more.