TomUK

Did post this in the UK forum but nobody else seems to have had the same problem.

Between about 20-30mph, on light throttle the engine/transmission of my 2006 RX400h makes a low groaning sound, sending a vibration through to the cabin. The engine just seems to be very rough at this speeds, like the engine is labouring. After exactly 30mph, everything is very smooth. It is also very smooth when running in EV mode at any speed.

The harshness/vibration only comes on when accelerating, so have ruled out tyres etc. The mileage is 85,000, and it has had a recent major service at a Lexus dealer. I use premium fuel.

The Lexus dealer had a look at the car for 1 hour and inspected the exhaust, engine mountings etc. but could find no faults. I went on a test drive with the service technician and he did notice the vibration.

The dealer said I will need to let them have the car for a whole day for them to try and find the cause, but I'm a little hesitant about paying for this as there is no guarantee they will find the problem.

Has anyone noticed a similar problem, or have any idea what the issue could be? Would be very grateful for any ideas.

LazarusLng

Try resetting the computer. Unplug the battery for 30 mins. See what happens over the next few days... How old is the battery?

smassey321

Years ago I remember reading a TSB that talked about a surge at 40 mph. Perhaps that is causing your vibration. A software update fixed it. Have you dealer confirm that you are on the latest software.

https://www.clublexus.com/forums/hyb...urge-tsib.html

My 06 will sometimes make some noises/vibrations if I keep the gas pedal at a constant position. I vary my pedal position often as I know how to drive it smother than it can do itself.

TomUK

My new commute has me driving at about 20-30mph the whole way in a line of slow-moving traffic, going from one set of lights to the next. Out on the main highway, when I am able to accelerate a lot more quickly, I barely notice the vibration at all. Just had a ride in a friend's Toyota Yaris (1.3L 4cyl) today which was much smoother than my V6!

The car is going to Lexus for a new water pump next week, have agreed to pay for 2 hours labour to investigate the issue. I've asked them to check for software updates and have a look at the transmission mount.

TomUK

I upgraded the 12V battery as soon as I got the car 1 year ago. I will try unplugging the battery next week if the dealer can't find the source of the problem (which I suspect they won't!).

CARspec

If they charge a flat diagnostic fee and you get a loaner car, it might actually be the deal of the century. I'd go for it (just get it in writing beforehand I suppose). Good luck!

TomUK

They had an offer for a 'Winter Health Check' for 15 pounds (about 25 US dollars), so I took my car in for that and asked to go on a quick test drive with the technician. They took about 1.5 hours to do the health check and look for the source of the vibration, but couldn't find anything. They did however find a leaking water pump and worn lower control arm bushes!!

They then quoted me 264 pounds (413 dollars) to spend a whole day looking for the cause of the vibration. They said this was for 2 hours labour, but they would spend the whole day investigating if needed.

I'm getting the water pump done under the warranty next week, so I called them today and asked them to go ahead with the investigation for the vibration.

jakenbake

Most dealerships don't charge for the diagnostic as long as you have the problem repaired.

appiahtus

HI
I have the same problem on my RX400H. How did you get yours fixed.
thanks

ukrkoz

Tom you have a hybrid, right? For the love of god, do NOT disconnect 12V and if you have to, for any reason, make sure you have backup 12V connected to the system. Maybe even through power outlet in cabin.
If you need to reset ECM - it won't help anyway, - pull fuse #35 I believe in fuse box. It may be different for your year, but that's the one for my 2012 Highlander Hybrid.

Just take my word on this - do not disconnect 12V unless at gun point.
Btw, I have been chasing low speed rolling shudder on my HiHy for a year now. 94 000 miles. I ended replacing all engine mounts, as they were shot. New tires. It's still there. Rolling with engine off, between 23 and 36 mph. Car jerks back fore.

seahamcw

Have got same problem. Mine goes in after the year Not holding out much hope as they had to put it up against another similar to tell if the diff had gone which I’d told them it had 2 weeks earlier. Point is I don’t just let things fester. It will be sortedeven if it costs them a new front end drive unit WARRANTY Keep posted what they find

thomas1

Have you found a solution to your problem? I too am getting this vibration?

seahamcw