94V8coupe

Car is new to me, bought it based on experience with another 1UZ powered vehicle (SC) - virtually trouble free from day one.
Kinda starting to hate this LS. Supposed "silky smooth" engine is anything but. It can be, but when it's not, it's annoying as hell.

Has the "low idle - vibration / rumble" situation, which appears to be common with these cars (who knew). This is an intermittent problem.
As the ambient temperature drops, I feel vibration while driving, almost like a throbbing sensation. A rhythmic vibration if that makes any sense.
It tends to diminish as the car warms up (10-15 minutes of driving). The vibration at idle can be felt throughout the drive, Other times very little or not at all.

I have gone through threads pointing towards engine / trans mounts, ECU, harmonic balancer but no real definitive answer (that I have seen).
Anyone out there been experienced any of this and actually fixed it?
I hate throwing parts (and money) at problems hoping for the best.

Does this sound familiar to anyone out there and have you fixed it?

deanshark

I'm right with ya. After I bought my 93 last Nov. (3rd LS400) and started fixing the stuff I knew was wrong, I started to hate it when it didn't fix what I thought the problem was.
Eh, I over paid and put way too many parts into it already, so I gotta start liking it again one of these days.
My low idle vibration (shake) is the engine mounts. I'm hoping cuz that's the next thing I change. If you put yours in Neutral when on the highway does the vibration almost disappear? Mine does. Mine also gets way worse when I hit about 80 MPH and almost none at 60.
You should at least, if you haven't already, change the tranny mount to see if maybe that's all it is. Cheap and easy enough. Also check your Harmonic Balancer for cracks in the rubber. Ya gotta look deep and hard to see cracks. I noticed mine in a pic after my T-belt job so I changed it thinking that was the shake.....but no. Just a little shake is gone but glad I changed it cuz I saw too many horror stories about them failing. (maybe 4 in the week before I did it)

94V8coupe

To be honest I have never really gone over much over 45mph (70kmph here in Canada) when this is happening.
It does more or less go away in neutral at idle but that opens other cans of worms. Is the rpm increase taking it out of the range where bad harmonics take over and cause the vibration? or is it because no forward gear is engaged removing the transmission itself from the equation? Something definitelty changes but what is it saying?

Hmmm... What you're talking about almost sounds like a wheel balance problem. I even had a wheel bearing behave kind of like that (different car).

Think I'm going to have to. If it makes any difference, good indicator that the engine mounts are done. Looks like PITA on this car. No surprise there.

Interesting. So no real improvement after the change. You need a puller for that I guess?

deanshark

Mine isn't a wheel balance problem, it shakes like hell at a stop in gear at idle. It sucks being heavy now cuz all my fat just jumps unless I put it in Neutral.
I narrowed mine down to motor mounts (I hope) and yes it's a PITA from ALL that I've read. That's why I keep putting it off. (I used to have a cat named Pita, ooo she was)
Tiny improvement from HB, but piece of mind is worth it to me. As for a puller, yes or no. Funny thing, I did the T-belt I didn't need a puller, it slid right off. But when I just changed the HB, I needed a puller. (rented from Autozone)

94V8coupe

What RPM are you turning at freeway cruising speed?

timmy0tool

iTrader: (7)

trans mounts on these car contribute to 70-80% of driveline vibrations as it's likely toast at anything higher than 100k miles. replace it and see what happens - cheap and relatively easy vs the engine mounts which are likely on their way out as well!

https://www.clublexus.com/forums/ls-...-question.html
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Losiracer2

You need to do the motor mounts and trans mount. Trans mount is about $50 at the dealer and Engine mounts are $140 each. Do this and all your problems will go away. Rubber is 20+ yrs old now, even the lowest mileage cars should have mounts done due to sagging. My trans mount on my 160k 99' was sagging by about 1" compared to the new one and was tearing. Driver mount was already tearing, Pass mount was sagging. You shouldn't feel any vibrations whatsoever at idle. This will 100% solve any NVH issues you're having at idle and should also help your highway vibrations. After doing just the trans mount, my highway vibs went away that I couldn't pinpoint, it effectively restored the driveshaft angle for the transmission. I did the engine mounts soon after that and it was nice and serene in the cabin again at lights.

deanshark

At 80 MPH I'm at 2200 RPM.
Under 1800 RPM it shakes pretty bad if I just touch the throttle, at any speed. But the lower the RPM the more it shakes with any amount of throttle, or in any gear.
Also, sometimes at a stop sign, it doesn't have launching power. I mean, I don't floor it like I'm at the track but if I try to take off quick it'll just creep and then start to go after it rolls a bit. (less strain on engine)

Edit;
Hey timmy0tool; Nice link for the tranny mount, with pics. Do you (or anyone) know of a motor mount tutorial that still has the pics? I've found a boatload of info and tutorials for the MM but the only one that had pics, they are all gone. (too old) Maybe it would help 94V8coupe, me, and others in the future. Thanks.

400fanboy

Rev the engine in park. In my car, it was quite smooth at idle. You start feeling it at 1500 and then above 2000 it's a rattlecan of vibrations from the motor. Any vibration signifies motor mounts.The allowable tolerance here is zero. With new motor mounts, you actually cannot feel the engine even if it's turning 4000rpm. All you will feel is the rotational torque to the body as the rev's increase. That's it. There is zero vibration or any signifier other than noise that the engine is running, you cannot feel it.

It becomes harder to diagnose while moving. So just park the car, throw it into park or neutral and rev the motor. Make sure the engine is warm, you don't want to rev a cold engine!

It's really difficult to describe the difference before\after motor mounts and transmission mounts can make. The car just seems to... calm down and glide a lot more effortlessly. It's tough to describe, but if they were broken, it's a night and day difference.

Do you think you could do me a favor and tell me about that story? A wheel bearing causing vibrations?

I ask because I'm chasing down a phantom vibration in my car for two years at this point. Been unable to determine it. It's like a wheel balance or road force issue, but that's been ruled out explicitly. Wheels are fine. Wheel bearing sucks because if that's the problem, you may as well just replace the whole knuckle, which means you may as well also want to replace the other links on that side of the car "while you're in there". Turns into a huge $$$$$$ spend. You replace basically all the rubber on that order, but it's still stupid expensive.

94V8coupe

Definitely seems to be the prevailing wisdom. Thanks.

94V8coupe

I hear you. This would be the first car I've ever owned that is so sensitive to aging motor mounts. I have had others where one or more were literally torn in two and never sent vibes like this into the cabin - front and rear drive. I know the Lexus mounts are an oil (hydraulic) and rubber combo ... I'm assuming they do a bit more dampening than your typical all rubber ones.

I will add this ... paid extra attention as i was out for a good drive yesterday, lots of traffic, lots of stops (shut downs and re-starts). I most definitely notice the vibes get weaker and weaker with subsequent shut downs (sit for a spell) and re-starts. To the point where it feels (to me) like it should (more or less). Any thoughts on that?

Losiracer2

its just that other cars aren't as well built as this, so the smallest NVH, you'll notice since there are no other rattles anywhere else. I might have one little creak from my driver sunvisor but that's pretty much all I've noticed in the 4 yrs of owning this car.

400fanboy

My center armrest creaks around the cupholder mechanism if it isn't put away or held down by something heavy. & if I'm honest the whole center armrest moves around a bit, it feels like the whole thing is loose.

And then big articulations at an angle to the chassis of the car (like in a driveway) can cause some noise from the rear trim I think.

That's it. 24 years old lol. I've been in brand new BMW's that are worse.

94V8coupe

This is not a small case of "NVH". It's annoying, it's obnoxious and not more noticeable because the rest of it is so solid
I find guys get a little fan boy-ish to the point they will make excuses for stuff they would rip any other car for.