M.Yasir

1998 Lexus LS 400- Engine vibration

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Hi

After driving a 2001 LS 430 just few days back, i realized that in my car i am missing the butter smooth ride quality, meaning there was no vibration felt in the cabin while the engine was running, super quiet cabin at idle and even while driving super quiet, you have to see the tachometer to check whether the car was in start condition or not

Comparing to my 98 LS 400 it turns out to be a generator, although i noticed a remarkable difference in ride smoothness when i changed my engine oil to 5W30 Total Quartz (earlier i used to dump in shell 20W50 multi grade due to the price, which now i feel was horrible and made a big mistake), i also changed the differential oil as part of a regular service

In neutral or parking gear when i bring the RPM to 3 or 4000 the steering shakes, while cruising at 85 MPH i can feel clear cut vibration at the steering wheel rest alone the whole body

I believe there is a lot of work balance to be done, now i am clueless from where to start either from suspension or from the engine mounts or just replacing the shocks will do the magic, bushings, ball joints etc

Now since almost 2 years of ownership i have replaced the following parts & Odometer stands at 262,000+ miles

  1. Starter Motor
  2. Spark plugs (all 8 nos replaced)
  3. Alternator
  4. Serpentine drive belt
  5. O2 sensors

Suggestions please

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I would imagine that any roughness at idle is emanating from the engine or a component of which is causing a dynamic imbalance.

One such area to investigate is the harmonic balancer crankshaft pulley as if this is defective it can cause a great deal of vibration through the vehicle.

Also, not sure if it has an over-running alternator pulley which can also cause issues which allow the drivebelt to deflect and cause vibration.

Timing belt one tooth out....?

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When was the last time to change engine mounts?

Brake torque the engine. If you feel or if you're able to see the engine hop up while doing so, I say start by replacing the engine and trans mounts.

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Thanks for the input

@Trevor Catt

Harmonic Balancer... i recently changed the serpentine drive belt and while in the process each and every pulley was turning effortlessly, is there a way specific way to check it

Over-running alternator pulley? how do i check that, but even before i replaced my alternator with a new one that car had the same amount of vibration

Timing belt one tooth out....... well i cannot say since the belt was replaced centuries ago, i am attaching a picture but it is not clear since the date of replacement is faded off

@Yamae

Engine mounts, my guess would never, most probably it has been running on the same mount since 1998, same applies for the trans mount

@Lexus_DK

You mean to say put in parking gear and rev the RPM and check the motor if it jumps or moves, hmmm i will do it today and will try to post a video

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Over-Running Pulley - How to test:   https://www.gatestechzone.com/en/problem-diagnosis/accessory-drive-system/oap-function-tests   Be aware, your car may not be fitted with one but it is good to see if it has and test for defect, if fitted.

Harmonic Balancer - How it works:   http://auto.howstuffworks.com/harmonic-balancer.htm   These can be damaged by incorrect removal in the past, and you would see the pulley deflecting but easiest way to test is to remove the belts and run the engine to see if the vibration has lessened.

Timing Belt:  If in doubt, replace as a matter of urgency if overdue before it fails and destroys the engine

 

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Sorry forgot to attach the photo of the timing belt record sticker, its difficult to read

Overrunning of the alternator pulley is highly unlikely since i installed a brand new alternator which came with the pulley

1998_LS_400-_Timing_belt_record_sticker.jpg

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With engine running, make sure the parking brake is on, to lock up the rear wheels. With your left foot constantly on the brake pedal, shift the gear selector in drive. With your left foot still on the brake pedal, quickly rev the engine by stepping on the gas pedal with your right foot. You don't want to hold the gas pedal down, just give a quick rev up to no more than 3K-4K rpm.

 

Then you can also do it in reverse. Just make sure your left foot is never off the brake pedal.

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hmmmmm...... and hey i did the same as @Lexus_DK advised, and man the motor was about to jump right off from the bonnet! i am almost 100% sure that the mounts which are currently in place have become stone and their date of birth is 1998!

Top priority is motor and trans mount

@billydpowell

4 mounts?

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Hi All

Long time i am posting, anyway following up with the above post, i replaced the 2 engine mounts and 1 trans mount along with trans filter and wow

Car is smooth like butter, and yes the old mounts were broken and completely deteriorated. anybody having LS 400 with 200k+ miles i would highly advise to replace these mounts to make a difference

Check out the pics

1998 LS 400- Engine Mount.jpg

1998 LS 400- Engine Mounts new.jpg

1998 LS 400- Trans mount installed.jpg

1998 LS 400- Trans mount.jpg

1998 LS 400- Underneath view.jpg

1998_LS_400-_Engine_Mounts-old.jpg

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