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New ls400 questions?

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Old 10-10-16, 07:13 PM
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981uz
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Default New ls400 questions?

Hi all, just picked up and ls400 1998 just wanted to no if some things are normal for the car.

-SUPER sensitive throttle.
-Car does not move forward on its own it takes a little bit of throttle.
-Car was sitting for a year with out really being touched so when i first started driving it the car was vibrating harder than i ever experienced in my life even the hood was shaking but then it went away as i increased speed and it never returned after that been trying to replicate it but never did again.
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Old 10-10-16, 07:36 PM
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Originally Posted by 981uz View Post
Hi all, just picked up and ls400 1998 just wanted to no if some things are normal for the car.

-SUPER sensitive throttle.
-Car does not move forward on its own it takes a little bit of throttle.
-Car was sitting for a year with out really being touched so when i first started driving it the car was vibrating harder than i ever experienced in my life even the hood was shaking but then it went away as i increased speed and it never returned after that been trying to replicate it but never did again.

1.) No, not really.
2.) Check for frozen brake calipers. Drive the car a bit and feel each wheel to see if one is hotter than the other. It should move easily without throttle input.
3.) LS400 vibrations are usually the rear transmission mount having separated.
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Old 10-10-16, 07:53 PM
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I really appreciate the help I will certainly look into your suggestions. Also the vibrating was coming from the front if that makes any since. Unless it was in my head and the whole car was shaking and as i increased speed it went away. I cant get the car to do it again i was thinking it could be the tires are not balanced correctly anymore. Or the breaks were getting rid of some rust maybe from sitting so long?
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Old 10-10-16, 09:00 PM
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Originally Posted by 981uz View Post
I really appreciate the help I will certainly look into your suggestions. Also the vibrating was coming from the front if that makes any since. Unless it was in my head and the whole car was shaking and as i increased speed it went away. I cant get the car to do it again i was thinking it could be the tires are not balanced correctly anymore. Or the breaks were getting rid of some rust maybe from sitting so long?
If the tires are not balanced it will vibrate as you go faster. When my tires were not balanced and I was going at 75 mph I will start to hear it and as I hit 80 it was pretty bad.
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Old 10-11-16, 06:12 AM
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Originally Posted by 981uz View Post
I really appreciate the help I will certainly look into your suggestions. Also the vibrating was coming from the front if that makes any since. Unless it was in my head and the whole car was shaking and as i increased speed it went away. I cant get the car to do it again i was thinking it could be the tires are not balanced correctly anymore. Or the breaks were getting rid of some rust maybe from sitting so long?
If your car had been sitting on it's tires for a year, then they would have been fairly flat on the bottom side of the tires. As you tried to drive, those flat sided tires would have thumped along until they returned to a more normal shape. Quite normal.
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Old 10-11-16, 06:34 AM
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You don't say what you did to prepare to drive it.
Fluid change would be good for sure. What maintenance has been done?
Throttle body cleaning?
Plugs?

I'm fairly certain the flat spot on the tires was the initial vibration problem, but other items probably need to be addressed.
Congrats on the purchase and welcome to the club.
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Old 10-11-16, 12:02 PM
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I'm sure you already know this, but with any car that has been sitting for a long time you need to do some basic inspections as well as procedures before expecting it to be a street ready rig. The seals and gaskets in the motor need to stay wet otherwise they dry out and can crack, or separate from their perches and cause you a TON of issues.

Check and ideally change the fluids- Your oil and trans fluids will have all settled and started to get a bit more viscous. The coolant could have scaling and deposits that are now built up. Look at the power steering fluid and brake fluid too. You will 100% want to change atleast the oil.
Fuel line, pump, filters... maybe even injectors. After sitting for a year the fuel will start to varnish. Sensitive throttle could be a result of a fouled portion of the fuel system.

Good luck with it.
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Old 10-11-16, 03:31 PM
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I guess no one is old enough to remember what flat spotted tires feel like. Old bias plys where good for that. It feels like the out of balance condition but after they hammer out and heat up, they run smooth. I have felt tires do that if they sit for awhile, yes radials.
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Old 10-13-16, 10:32 AM
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I can only offer my own input, mine was only driven about 3k miles in the past 4 years before I bought, as a result tires were terrible, even though tread depth was acceptable. First thoughts I honestly had were bad engine or trans mounts due to the severe vibration. I could only stand it for a few weeks before replacing, it made a world of difference. I also found brakes took some time to come back into their own, not exactly what you would call frozen, but definitely made some noise for a few weeks.
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Old 10-13-16, 12:49 PM
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Not going to try diagnosing a car in this condition. You need to go through the fluids including the trans, replace filters and oil, and confirm the tires aren't too old (or dry rotted).

(Tire aging information: http://www.tirerack.com/tires/tirete...jsp?techid=138 i you live in a hotter/brighter climate I would replace loser to 8 years not 10).


Get the car caught up on servicing and we can tell you what's normal/not.

Throttle sensitivity is no unusual for those unaccustomed to electronic throttles, the rest of your issues are possible symptoms.
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Old 10-16-16, 12:53 PM
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it's not that the throttle is necessarily super sensitive, the engine just has super amounts of low end torque. everyone who first drives one of these has that same "complaint" about the car. just be very gentle on the initial driving away and eventually you'll just get used to it and be fine. now both 1 and 2 on your issue list can be fixed with same solution. the car not moving forward on its own will happen if the idle is slightly lower than it should be. in N idle speed should be about 750 rpm, and in D about 500 rpm. if the rpms are too low in the car wont creep forward like it's supposed to.

make sure the throttle body isn't too caked in dirt, and make sure the throttle cable itself doesn't have any slack in it. these cars have electronic throttle control but there's still a physical cable that operates the "accelerator pedal position sensor" and if there's too much slack in the cable it wont actuate the throttle as smoothly as it should. just look up LS400 clean throttle body or something like that and there should be a bunch of results. another way to make the car creep forward better is to either turn the headlight switch up 1 click (no need to turn the headlights themselves on but just 1 click up for the tail lights and interior lights) or to turn the A/C on because both of these will increase the throttle opening ever so slightly to compensate for the increased parasitic draw from the alternator or A/C compressor.
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Old 10-17-16, 04:15 PM
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So I really appreciate everyone responding me and helping me out. Been driving the car for a week and the car now is running MUCH more smoothly either i got used to the throttle or that also is alot better tires are dry rotted so will be replacing soon. The car also moves its self forward with ease turns out it was just the breaks were very rusty. Got the car inspected they said the car surprising is a solid as a bullet they said there never seen a car in such good condition for its age.

The battery needs to be replaced, steering rack is leaking, needs breaks, needs tires, needs windshield wipers, needs a front end alignment and fluids and filters need to be changed.
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Old 10-18-16, 10:24 PM
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looks very nice, has the shaking stopped after using the brakes some more?
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Old 10-20-16, 10:50 PM
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So if those are the same tires that all the vibration was happening with I was right on then about the flat spots.
And actually jaaa mentioned it first, he's the man on this one. I didn't see his post and he beat me on this one.
I'm surprised Billy didn't get it first this is something older guys know all about.

Last edited by dicer; 10-21-16 at 12:35 PM. Reason: Major correction
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Old 10-21-16, 08:06 AM
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Originally Posted by dicer View Post
So if those are the same tires that all the vibration was happening with I was right on then about the flat spots. Yeah I'll just blow my own whistle no one else will.
I guess you just skipped over my post.
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