1999 Ls400 Engine Vibration Between 1800-2200rpm

[caspers-flight]

Hi all and thanks for any help you may be able to assist me with. Great site!

Its a 1999 LS400 and has been to lexus twice. It has approx. 114k and has a vibration when the throttle is between 1800-2200rpm, whether it is in park or going down the road in any gear. The motor mounts have been change and the vibration got better but is still there. It is enough to drive you crazy while going on a 600 mile road trip or just driving around town. If there is anyone with knowledge to this problem it would be helpful.

[burgundy]

have you checked your spark plugs or got any fault codes

[marcus]

i would say take alook at all the plugs, you could have 2 or 3 that are not fireing,

[Leadfoot]

i would say take alook at all the plugs, you could have 2 or 3 that are not fireing,

The 1998-2000 models you have a single igniter per spark plug. Everything is checked by the computer during running and it will detect misfire in each cylinder and store a fault code. Get somebody with an OBDII fault code reader to check. I would be very surprised if it was plugs, but if they are due for changing nothing wrong with forced maintenance.

On the earlier cars the engine, transmission and also the diff mounts could give trouble. Since you have changed the motor mounts and saw improvement, did the trans mount get done too? Won't be the diff though because you said it happens in park too. The fuel injection system has a cutout at the 1800 rpm mark, I wonder if its a fueling problem. Fault codes would report that too.

Hope you track it down....

[caspers-flight]

i would say take alook at all the plugs, you could have 2 or 3 that are not fireing,

The 1998-2000 models you have a single igniter per spark plug. Everything is checked by the computer during running and it will detect misfire in each cylinder and store a fault code. Get somebody with an OBDII fault code reader to check. I would be very surprised if it was plugs, but if they are due for changing nothing wrong with forced maintenance.

On the earlier cars the engine, transmission and also the diff mounts could give trouble. Since you have changed the motor mounts and saw improvement, did the trans mount get done too? Won't be the diff though because you said it happens in park too. The fuel injection system has a cutout at the 1800 rpm mark, I wonder if its a fueling problem. Fault codes would report that too.

Hope you track it down....

Thanks, the transmission mounts are next. I forgot to mention that the LS had the 60k service done last time it was at Lexus....so that would cancel out the spark plugs. I appreciate all you guys have suggested.

Is it possible that the transmission could cause this when the motor is in park and you are running the motor at 1800-2200 rpm? Does the transmission turn at all to cause this vibration??

[Leadfoot]

Is it possible that the transmission could cause this when the motor is in park and you are running the motor at 1800-2200 rpm? Does the transmission turn at all to cause this vibration??

The trans is bolted solidly to the motor, so even though the lexus V8 is a very smooth unit and has very little shake, if the motor moves so will the tranny. The torque reaction of revving the motor causes some rock. I think the clue about the 1800-2200 rpm is a vital, have you had the codes read?

[beedunkn]

Hi all and thanks for any help you may be able to assist me with. Great site!

Its a 1999 LS400 and has been to lexus twice. It has approx. 114k and has a vibration when the throttle is between 1800-2200rpm, whether it is in park or going down the road in any gear. The motor mounts have been change and the vibration got better but is still there. It is enough to drive you crazy while going on a 600 mile road trip or just driving around town. If there is anyone with knowledge to this problem it would be helpful.

I actually joined this forum for this problem exactly! I've got a 1999 LS400 with 112k. My vibration occurs exactly like yours does. I've changed plugs and tires (running Michelin Primacy now) and still hear the rumble. It is irritating on the road! I did not chage wires however. Does anyone think the wires could be the culprit?

[Spinakerr]

Hi all - I had the same problem on my 1995 mk2. We checked everything (took many, many weekends). In the end it turned out to be a split front suspension spring that hadn't fully broken but vibrated horribly at those revs. It was patently a freak occurence but worth checking! Dig out you torch and have a 5 second check.

[Marcel53]

My 2000 LS400 had the oscillation problem replaced the transmission mount. The difference feels like day and night. Cost was 54 part 85 labor.

[Malc]

................. sad about your issues guys BUT hey it's wonderful to see so many new faces appearing at long last

All these issues are relatively simple to resolve I'm sure ( but I know not how specifically ) and after 18 years of driving my  Ls Mk1, then 2 and now 3 and for a couple of hundred thousand miles I can assure you all that these are just FABULOUS and RELIABLE cars to have and to cherish

Long may all your and our problems be of some inconsequence and inexpensive to resolve 

Malc

[Bluesman]

When I had a similar problem as you it was an Oxygen sensor causing a miss fire.