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Can You Feel The Engine Is Running At Idle?


qha_vn
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ls400 '90, i feel the vibration when touching steering wheel or shifter when engine runs idle at P

i am wondering if the engine mounts are bad. its original with 100k miles

I have that vibration as well through the steering wheel on my 1991 LS400. It has 210K and I am sure that is the engine and/or transmission mounts. My 1990 old LS400 did NOT have any vibrations through the steering wheel at any time... smooth as silk, but I think all of the mounts had been replaced on it.

So yes, with proper mounts a gen 1 LS400 should be as smooth as a brand new LS.

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FWIW, I just had my engine mounts replaced, but have not gotten around to doing the transmission mount myself yet. it is also worth mentioning i broke a couple of sockets trying to use the "starter trick" to get my crank pulley off, so my motor mounts were certainly shot. my observations on a 1993 with 130k:

before motor mounts: i had bad vibration in the steering wheel, shifter knob and particularly seat at ~400RPMs, where my car usually idles. In certain conditions when it idles at 600 the seat vibration went away, steering wheel and shifter knob had a consistent much less pronounced vibration not noticably affected by RPM. Similar vibrations in 100 rpms windows every few hundred rpm.

after motor mounts: seat vibration is GONE. I don't feel the engine anymore at all in the cabin below 1500RPMS. at 1800rpms the seat vibration comes back for 100rpm windows every few hundred rpm, only really noticeable in park or neutral. I suspect that with the engine running at that speed it's transmission vibration I'm feeling in the seat. steering wheel and shifter knob completely unaffected, but the vibration is really very slight.

so my best guess is that if you've got steering wheel, shifter or seat vibrations @ ~1800rpms in park, you should probably start with just the transmission mount and see if that takes care of your issues. If you've got vibration down closer to idle the engine mounts are due.

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You can get a much better deal by buying your mounts through one of the online vendors, instead of the dealership. lexuspartsonline.com or something similiar. I would caution the ebay stuff. They might look like oem, but don't be supprised if they don't perform like oem. I ran into this with driveshaft flex couplings a few years back. While you're at it, you might as well spend the extra $20 for the tranny mount too, as all three of these mounts tend to play together. Two motor, one tranny. Yes, if you're feeling vibrations like that, then it's time to replace the mounts. Time plays a bigger role in the condition of these mounts than does mileage. I replaced mine on my 95' at the 98k mark, and it made a world of difference. Additionally, for not that much money "maybe $20 tops", you can replace the rack's steering grommets too, which will insulate the rack from the frame of the car. There are two of them, one on each end, and it's a very easy DIY, just like the tranny mount.

Buy the parts online, and then take them to your favorite indi mechanic to have installed. YOu'll probably pay around $80 per motor mount for installation "the driver's side is a real !Removed! to deal with". The rack and tranny mount you can do yourself if you like, or have them put them in too. They're very easy.

You'll love the difference, trust me.

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Sounds super! I cannot wait until I can get mine replaced... engine and tranny mounts that is. Never knew about that rack grommets... is there any chance that changing those could lead to that common rack leak?

You can get a much better deal by buying your mounts through one of the online vendors, instead of the dealership. lexuspartsonline.com or something similiar. I would caution the ebay stuff. They might look like oem, but don't be supprised if they don't perform like oem. I ran into this with driveshaft flex couplings a few years back. While you're at it, you might as well spend the extra $20 for the tranny mount too, as all three of these mounts tend to play together. Two motor, one tranny. Yes, if you're feeling vibrations like that, then it's time to replace the mounts. Time plays a bigger role in the condition of these mounts than does mileage. I replaced mine on my 95' at the 98k mark, and it made a world of difference. Additionally, for not that much money "maybe $20 tops", you can replace the rack's steering grommets too, which will insulate the rack from the frame of the car. There are two of them, one on each end, and it's a very easy DIY, just like the tranny mount.

Buy the parts online, and then take them to your favorite indi mechanic to have installed. YOu'll probably pay around $80 per motor mount for installation "the driver's side is a real !Removed! to deal with". The rack and tranny mount you can do yourself if you like, or have them put them in too. They're very easy.

You'll love the difference, trust me.

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i will order 2 engine mounts, 1 tranny mount and steering rack grommets. i agree that age plays more important role in rubber parts life then the miles do. cant wait longer

Thanks all for your comments especially convincible post by nc911 ;-)

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is there any chance that changing those could lead to that common rack leak?
definitely not

Thanks. I just wanted to be sure that there would not be enough movement to cause seals to shift and bind.

The only way I could see a leak being caused by the new gromments would be during the installation. I wouldn't move the rack too much, just lift it up maybe 1/4 inch to remove the old gromments and install the new ones. If you look at the rack, on each end there should be a U shaped clamp. The gromments are the rubber pieces that those U shaped clamps attach down upon. It's very similar to your stabilizer bar bushings in terms of use. The best thing to do to avoid the rack leak is to make sure your power steering solenoid screen is nice and clean, and the fluid is in good order. That screen gets dirty, and it creates back pressure on the whole system, which will force the liquid to find it's way through your seals and to your driveway.

On mine, I knew the engine mounts were bad due to engine vibration and noise coming into the cabin, plus, a noitcable thump at startup, which was the driver's side mount hopping up and down with the engine's torque. All of these were elimenated with the new mounts. Quite honestly, the new mounts gave the car a new feeling. The engine was totally insulated from all noises and vibrations, and it just made the car smoother. It's not a cheap repair, but one well worth the money. In my opinion, the mounts are one of the biggest improvements you can make on the LS series. ;)

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Thanks for the tips! I will have that screen checked at the dealer soon.... may have those grommets changed there as well. I want to get new mounts ASAP, because my vibration is getting worse and its almost unpleasant to drive now.

is there any chance that changing those could lead to that common rack leak?
definitely not

Thanks. I just wanted to be sure that there would not be enough movement to cause seals to shift and bind.

The only way I could see a leak being caused by the new gromments would be during the installation. I wouldn't move the rack too much, just lift it up maybe 1/4 inch to remove the old gromments and install the new ones. If you look at the rack, on each end there should be a U shaped clamp. The gromments are the rubber pieces that those U shaped clamps attach down upon. It's very similar to your stabilizer bar bushings in terms of use. The best thing to do to avoid the rack leak is to make sure your power steering solenoid screen is nice and clean, and the fluid is in good order. That screen gets dirty, and it creates back pressure on the whole system, which will force the liquid to find it's way through your seals and to your driveway.

On mine, I knew the engine mounts were bad due to engine vibration and noise coming into the cabin, plus, a noitcable thump at startup, which was the driver's side mount hopping up and down with the engine's torque. All of these were elimenated with the new mounts. Quite honestly, the new mounts gave the car a new feeling. The engine was totally insulated from all noises and vibrations, and it just made the car smoother. It's not a cheap repair, but one well worth the money. In my opinion, the mounts are one of the biggest improvements you can make on the LS series. ;)

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This is a good thread. I had my tranny mount replaced a few months ago and it made a noticeable improvement, but I'm still experiencing what others here are. I'm having the motor mounts replaced next week and will post an update here.

Bali26: Are those the steering rack grommets? Also, do you have part numbers for them?

Thank you.

Eddie

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I've been reading up a bit on replacing these mounts as I believe that’s what is needed on my car. I have a '90 LS with 132k on it. I am positive the mounts are original as the previous owner turned out to be a bit of a flop on the maintenance. I have noticed in the last few trips home from school (about 400 miles) that after re-accelerating back to highway speeds (60-75mph) my car gets a terrible vibration in the seats, shift knob and steering wheel. The vibration slowly works its way out and after 3 or 4 miles the vibration is gone. This does not happen when going from a stop up to speed, but happens when I go from 60-75, then slow down considerably and then speed back up, which is very typical in rush hour traffic. I believe this is due to a bad tranny mount but would like to hear your guys input before I jump in and start replacing parts.

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This is a good thread. I had my tranny mount replaced a few months ago and it made a noticeable improvement, but I'm still experiencing what others here are. I'm having the motor mounts replaced next week and will post an update here.

Bali26: Are those the steering rack grommets? Also, do you have part numbers for them?

Thank you.

Eddie

Oh no they are the front and rear sway bar bushings...

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That's what I thought. Thank you.

Eddie

This is a good thread. I had my tranny mount replaced a few months ago and it made a noticeable improvement, but I'm still experiencing what others here are. I'm having the motor mounts replaced next week and will post an update here.

Bali26: Are those the steering rack grommets? Also, do you have part numbers for them?

Thank you.

Eddie

Oh no they are the front and rear sway bar bushings...

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