Rx400H Rough Engine/transmission

tom123 · September 26, 2014

Have started to notice my 2006 RX400h doesn't seem as smooth as it once was. Has done 80K. Not sure if it's the transmission or the engine, but from pulling away up to about 30mph the powertrain seems quite rough and there is more vibration than I would expect. It's hard to describe, but it seems like a rough groaning sound/sensation when accelerating. At speeds above 30mph everything is smooth.

Doesn't seem to be anything to do with the steering or wheels/tyres. I thought a recent main dealer service/oil change would help but it made no difference.

Have just driven a CT200h loaner while my RX was having an MOT, and was surprised to find that the 4cyl engine was much smoother.

Anyone experience anything similar or have any idea what it might be?

Boxbrownie · September 26, 2014

I believe there was an issue with one (the forward one I think) of the engine mounts at some time, but first thing is to check that the engine really is firing on all six cylinders (it is easy with a multi cylinder engine to assume every cylinder is working but actually easy to to miss if theres a problem on just one cylinder) then check the mounts.

tom123 · September 26, 2014

Thanks for the reply, will probably have to go back to the dealer to get those things checked. Looks like another £54 diagnostic charge will be due.

Although would have hoped they would have picked up a cylinder problem during a major service?

Boxbrownie · September 27, 2014

They certainly should have picked up a misfire during service checks, so it could point to another fault, maybe the engine mount but I hope they do not charge you £54 for looking at the mount before they decide!

Did you mention the vibration to them when you took it in for the service?

Romasato · September 29, 2014

Yeah, I am noticing the same on mine - so not sure. Would £54 Lexus diagnostic detect misfires? How would they check for that? I thought a service light would come on or something if a fault like this is detected by the sensors?

Boxbrownie · September 29, 2014

It should be detected yes, but obviously somethings not right and easiest to eliminate the obvious first then work back.

tom123 · September 29, 2014

I didn't mention it at the time of the service because I thought an oil change would fix it (plus I was more concerned at the time that they fixed a really annoying clanging sound - which turned out to be the bonnet/hood lid mechanism needing adjusting).

Diagnostic charges seem to vary from dealer-to-dealer, plus they won't charge you if they find something wrong that they will then go on to bill you for if you get it fixed there. I once took my car in because the aircon wasn't cold enough, they tested it and re-gassed it and just charged me a £54 diagnostic fee.

Anyway, I'm going to take the RX back in next week to hopefully get the aircon fixed properly, and will get them to have a look at it then. I will post the outcome next week!

Parrot of Doom · October 2, 2014

I would have thought a mis-firing cylinder would have immediately triggered a code, resulting in the engine warning light illuminating. And I think you'd have noticed it immediately, since mis-fires tend to be rather dramatic.

tom123 · November 26, 2014

Still haven't found the cause to the problem. Got one Lexus dealer to take a look whilst it was in with them having the air con repaired. They couldn't find anything wrong with the car, and told me there's 'nothing serious' wrong with it.

Just took my car in to a different Lexus dealer for a Winter Health Check (£14.99) and asked the technician to go on a quick test drive with me. He could feel the vibration I was noticing through the accelerator, and said he will look at the engine mountings etc. whilst doing the health check.

Anyway, he didn't find the cause. They had the car for about one and a half hours. He told me he looked at the mountings, exhast etc. Said it definitely wasn't an engine misfire.

Have been quoted £264 (2 hours labour) for them to undertake a more thorough inspection. They will need the car for a whole day. No guarantee of finding the problem though! The car is still under the approved used warranty, so am keen for a potential problem to be picked up, so might just go ahead and get them to take another look.

Just wondering what other people would do in this situation?

Basically, between about 20-30mph, on acceleration, the engine seems to make a groaning sound and transmits a vibration through to the cabin and accelerator pedal. Above 30, everything is smooth. It's quite a subtle sound/vibration, and only really noticeable from the driver's seat. However, the engine definitely isn't as smooth as 4cyl cars that I have driven. Sorry for the long post!

Animal Mother · November 26, 2014

Bad fuel?

tom123 · November 26, 2014

Aways use BP ultimate or Shell V-power petrol, might try running a couple of tanks in a row of each one though. Thanks for the suggestion.

mikeyv · November 26, 2014

So, the car is under warranty, and they agree there is a vibration.

It's their job to find and fix the fault surely, so why would you be expected to pay them anything at all?

tom123 · November 26, 2014

So, the car is under warranty, and they agree there is a vibration.

It's their job to find and fix the fault surely, so why would you be expected to pay them anything at all?

I did think the same thing myself! They did confirm that if they found a fault that they were asked to repair, there wouldn't be a diagnosis charge.

Had a similar problem when I had a clanging sound at the front of the car. Was quoted £54 for half an hour labour, but they couldn't find the problem in that time. When I asked them how long they thought they would need, they said 'we could take 6 weeks to strip the engine sir.' Got them to do the major service a couple of months ahead of scedule instead, and they found and fixed the problem for free (the bonnet catch was loose, causing it to move up and down slightly over bumps in the road).

At least this time they have given me a fixed price to spend a day searching for the problem. If they still can't find it after that, I think that I will just have to live with it.

jonthebarber · November 26, 2014

Hi

Shot in the dark , but my 05 rx300 started a similar problem , it felt like a prop failing issue (experienced this with a vw Touareg) whipped it to my mate , on the ramp searched underneath, nothing , turned out to be a egg on the tyre where the grip is , new tyre and problem solved . It felt worse at lower speeds

Jon

tom123 · November 27, 2014

Hi

Shot in the dark , but my 05 rx300 started a similar problem , it felt like a prop failing issue (experienced this with a vw Touareg) whipped it to my mate , on the ramp searched underneath, nothing , turned out to be a egg on the tyre where the grip is , new tyre and problem solved . It felt worse at lower speeds

Jon

Vibration goes as soon as I lift off the accelerator, and only comes on when accelerator is applied, so wouldn't have thought it was the tyres, but will have a look at them to be sure.

nelmo · November 29, 2014

Is it possibly just because you are getting used to the car?

When I first got my RX, I was amazed by the refinement and smooth ride. Gradually, I've got so used to it, that I'm noticing more subtle noises and I've convinced myself a couple of times that something is loose/rattling.

A solution is to drive a few lesser cars (I've been in a Transit for the last week) - makes my RX feel like a magic carpet again :)

tom123 · November 30, 2014

Is it possibly just because you are getting used to the car?

When I first got my RX, I was amazed by the refinement and smooth ride. Gradually, I've got so used to it, that I'm noticing more subtle noises and I've convinced myself a couple of times that something is loose/rattling.

A solution is to drive a few lesser cars (I've been in a Transit for the last week) - makes my RX feel like a magic carpet again :)

Actually, it was driving other cars that made me think there was something wrong with mine! There is a definite harshness there that I haven't noticed when driving several other (and much cheaper) cars. But I agree with you about noticing little noises due to the car being so quiet in general.

I'm now thinking it might be an issue with the transmission, as the engine is smooth when revving it in neutral. Not sure how much the lexus technicians would be able to look into the gearbox in a couple of hours though.

ColinBarber · November 30, 2014

do you notice it in electric only mode or just when the engine (ICE) is running?

tom123 · November 30, 2014

do you notice it in electric only mode or just when the engine (ICE) is running?

Only when the petrol engine is running.

It is very smooth when driving up to about 20mph, then it feels harsh until 30mph, then it feels very smooth again.

Romasato · December 13, 2014

Yeah, I get that mellow "drilling" fel effect now and then, but I don't mind it anymore - could say even enjoy it sometimes. I guess it is to do more with CVT than engine itself - or a link between both.

Parrot of Doom · December 13, 2014

Make a list of when the car vibrates and when it does not. That way you should be able to eliminate factors that couldn't be the cause.

If there's a transmission mount, check that. The vibration may be coming through the vehicle's floor. But if you can get the dealer to agree there's a problem, I would recommend they have a good long look at the gearbox and its internals, since that would appear to me to be the source of the issue.

http://www.vibratesoftware.com/html_help2014/2011/Diagnosis/Reference/Hybrid-Electric_Vehicles.htm

tom123 · December 13, 2014

Make a list of when the car vibrates and when it does not. That way you should be able to eliminate factors that couldn't be the cause.

If there's a transmission mount, check that. The vibration may be coming through the vehicle's floor. But if you can get the dealer to agree there's a problem, I would recommend they have a good long look at the gearbox and its internals, since that would appear to me to be the source of the issue.

http://www.vibratesoftware.com/html_help2014/2011/Diagnosis/Reference/Hybrid-Electric_Vehicles.htm

Thanks, that's a great website. Since the vibration/groaning sound only happens during light throttle from about 15-30mph, I'm starting to think it must be a transmission issue. I'm sure that a Lexus engineer who understood how the CVT works and when MG1/MG2 etc. came on would be able to tell instantly what the issue was, without even looking at the car, given the very specific speeds that the vibration happens during.

Anyway, car is going into the dealer on Friday for a new water pump. They are going to have another look at it then. I suppose a new CVT box would be £5000 plus? Not sure how much the dealer could take apart the transmission in a couple of hours, or even if they would feel like doing so at all!

tom123 · December 22, 2014

The car was booked in first of all on Friday and then today at Lexus Birmingham, but they have now called up twice to tell me that a technician is off sick and therefore they cannot do the work, and would I like to come back in the new year. Having already cancelled the appointment once, I would have thought that they would have made a bit of an effort to ensure it didn't happen twice.

Fortunately for me, I'm going down to the south west over Christmas, and will be staying near the Lexus dealer where I bought the car from. One quick phone call to them, and within a couple of hours they had arranged the warranty authorisation for the water pump and confirmed that they will fit a new timing belt for around 50 quid parts only. They have also agreed to go on a test drive to look at the vibration issue when I go there next week.

Will never go back to Lexus Birmingham, this is the second time they have messed me around like this. Rant over!

tom123 · February 7, 2015

Well after visiting three different Lexus dealers the problem seems to have been fixed.

Dealer No. 1 wanted £264 just to try and diagnose the problem.

Dealer No. 2 thought that the problem was due to a bad timing belt tensioner, so I had them replace it as it was in for a new water pump and timing belt at the time anyway. Made no difference at all.

Dealer No. 3 had the car in for a whole day to inspect it. The invoice says they have performed a 'systems reset and now tested all ok.' The car does now seem to be 90% better, with less vibration/groaning during acceleration at low speeds. They only charged a £57 diagnosis fee for the work which I was happy with.

I wonder if they have reset the transmission's computer, which had been causing the engine to labour under light loads. Sound logical?