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13 hours ago, Barry14UK said:

Earlier in thread OP said the problem became noticeable only after the engine had warmed so I think it very unlikely to be an injector.  When an injector is at fault the car tends to run noticeably rough from the outset and regardless of temperature.  I had this happen on an Opel many years ago (in the happy days when spark plugs were easy to reach) and luckily there was no difference when I disconnected the 1st plug lead I tried. I replaced the corresponding injector and all was well again.  Bradford were on the right track when they suggested trying an injector cleaner which can sometimes work but didn't in your case.

Unfortunately, as regards the problem the OP has, I can't come up with anything that has not been said already, although I am inclined to suspect a problem with the gearbox.  I am assuming there is no possibility of a caliper sticking which would be more noticeable with build up of heat.

Mine was intermittent. It wouldn't do it sometimes. The injector was faulty but not all the time. 

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On 6/3/2019 at 6:42 PM, rayaans said:

Mine was intermittent. It wouldn't do it sometimes. The injector was faulty but not all the time. 

I understand that injectors sometimes work intermittently but at such times as they are not working properly apart from roughness, even in a 6 cylinder engine, there would be a loss of power.  If this happened and I can't see it was mentioned, I wouldn't have thought the member affected would be looking at exhaust suspenders as the possible cause.

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Intermittent noises and vibrations are very difficult to locate and eliminate.

Try raising the car on a lift jack or on stands and put the engine on inspection mode whereby the engine runs continuously and you can vary the rpm with the accelerator.

If the symptoms occur under no load, you should be able to pinpoint what you are looking for.

For a GS 450H , the inspection mode is achieved as follows:

1. Turn the power switch ON (IG) .

2. Move the shift lever to P and then depress the accelerator pedal fully twice. [ If the shift lever is already at P position, just press the accelerator pedal twice ]

3.Move the shift lever to N position and press the accelerator pedal twice.

4. Move the shift lever to P position and press the accelerator pedal fully twice.

5. Check that " maintenance mode " is displayed.

6. Turn the power switch ON ( READY) and the engine should start.

7. To deactivate the inspection mode, turn the power switch OFF.

 

Wishing you the best of luck,

 

Chris.

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3 hours ago, Mihanicos said:

put the engine on inspection mode whereby the engine runs continuously and you can vary the rpm with the accelerator.

What is this sorcery of which you speak?

EDIT - Oops, just read further than that and found it :thumbsup:

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On 6/2/2019 at 6:42 PM, royoftherovers said:

I think he will report back Mark.

He`s had some sound advice.

Back home now from our 750 mile round trip to Northumberland. Thanks for all the posts and will try touching the brake pedal idea.

There were lots of times on the journeys there and back for the boom/thudding to show itself and as ever it was whilst coming off the throttle and the engine rpm dropping to around 1,000 rpm. Several really bad sessions when the vibrations really came up through the driver's seat into the cabin. This also happened in Alnwick and it was the worst its ever been. I wondered if we'd be in trouble for getting home. As if by divine intervention there was a phone call from Lexus Bristol the following morning saying that Lexus had agreed to replace the whole exhaust system ( including the large boomer box). This is booked in for next Thursday. I remain convinced that the exhaust system has something to do with the issues I'm facing but will be amazed if it cures everything. I live in hope.

Yesterday I had a Mitsubishi PHEV  for 24 hours but Jan's back was playing up and she couldn't get comfy in the passenger seat ( no adjustment possible ) and was in pain with her sciatica. The way the PHEV pulled away with no judder was wonderful but there's no comparison the the sheer comfort in the RX.

I'll post again when the exhaust has been replaced to say whether that was a waste of time and effort or not.

Thanks again,

Alan

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@stringbender I would advise caution here. If you've gone to them and explicitly asked them to replace the exhaust system, and they've agreed to do it in order to resolve your issue then as far as they are concerned that is the deal that makes this problem go away. Because you asked for a specific solution you may have no recourse if the specific resolution you've asked for doesn't fix the problem. You should never do this when taking your car to garages - always make them diagnose the car first so that if whatever they do to fix it doesn't work you have recourse.

Really your position to Lexus should be "the car is doing something it shouldn't, i want it fixed". Since they are apparently not able to diagnose it, perhaps you should start by having it diagnosed somewhere else. If the vibration is as noticeable as you said it is today then it should be no trouble for a competent technician to figure out what's causing it. You shouldn't settle with them over a guess, you're giving too much away. It's their responsibility (legally, under consumer law) to fix it or take it back.

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17 hours ago, m4rkw said:always make them diagnose the car first so that if whatever they do to fix it doesn't work you have recourse.

You shouldn't settle with them over a guess, you're giving too much away. It's their responsibility (legally, under consumer law) to fix it or take it back.

Thanks for that advice Mark. I'll be on my guard now if they want me to sign anything that might terminate my rights. I've said before that this whole business has got the better of me and I feel really stuck as I can't expect them to drive the thing long distance to try and experience what's bugging me. 

Alan

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12 minutes ago, stringbender said:

Thanks for that advice Mark. I'll be on my guard now if they want me to sign anything that might terminate my rights. I've said before that this whole business has got the better of me and I feel really stuck as I can't expect them to drive the thing long distance to try and experience what's bugging me. 

Alan

Just make sure you explain that you want the vibration fixed, not that you specifically want them to replace the exhaust. Make them take ownership of what the solution is and commit to fixing the vibration.

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1 hour ago, m4rkw said:

Just make sure you explain that you want the vibration fixed, not that you specifically want them to replace the exhaust. Make them take ownership of what the solution is and commit to fixing the vibration.

Sound advice indeed.

It is not for the man on the Clapham Omnibus to tell the Driver what to do !

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1 hour ago, royoftherovers said:

Sound advice indeed.

It is not for the man on the Clapham Omnibus to tell the Driver what to do !

I’ve no idea what you mean! 

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1 hour ago, m4rkw said:

I’ve no idea what you mean! 

Does the man in the street have the competence of the professional Mark?

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14 minutes ago, royoftherovers said:

Does the man in the street have the competence of the professional Mark?

Nope, exactly why a diagnosis from a qualified technician is necessary. If you go to a garage and ask them to replace something they will do exactly as you ask and if it doesn’t fix a problem you didn’t tell them about then that’s your problem. I know this because I’ve made this mistake myself and wasted a lot of money!

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I once had a B5 passat diesel that had an annoying issue from a cold start. At first it would run fine but as soon as you drove a few feet it would start stumbling every few seconds, the rev needle would dip every 2-3 seconds and occasionally it would just cut out. Once warmed up it ran fine and my local VW specialist couldn't figure it out. I bought a VCDS cable and graphed a ton of data from the ECU trying to work out what it was but despite handing all of that over to a technician on paper they couldn't figure it out. So eventually I decided to take it to a diesel specialist and by that point I was convinced it was a problem with one of the injectors. I asked the diesel specialist (who specialise in refurbishing injectors) to remove and test the injectors. Of course they told me all four injectors needed refurbishing (which they may well have needed at that kind of mileage) so I asked them to go ahead, and of course it didn't fix the problem. Over £1000 spent and still had the same issue, car ran exactly as before, and I had no recourse at all because I'd asked them to test and refurbish the injectors and *not* to diagnose the issue for me. I ended up selling it without ever knowing what the problem was.

An expensive lesson but hopefully @stringbender can benefit from my mistake and not do the same thing!

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7 hours ago, m4rkw said:

I once had a B5 passat diesel ....

An expensive lesson but hopefully @stringbender can benefit from my mistake and not do the same thing!

I've owned 2 Passat estates in the past. Both were petrol engines but I remember how they used to practically die on you as you took off a bit smartish to get out of a junction. I used to think that at tickover they were running on almost fresh air ! Scary at times. I forgot all about that as soon as I moved to the RX300. Plenty of power at the ready to get you out of trouble. 

Alan

 

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@stringbender good luck tomorrow Alan. I would suggest when you go in asking them explicitly if they are *sure* that replacing the exhaust is going to fix the problem. If they yes - great, you can hold them to it and pursue further if it doesn't. If they say anything other than yes I would insist on the problem being correctly diagnosed first, and if they aren't able to do that then have someone else do it and then go back to them and demand they reimburse you.

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3 hours ago, m4rkw said:

@stringbender good luck tomorrow Alan. I would suggest when you go in asking them explicitly if they are *sure* that replacing the exhaust is going to fix the problem. If they yes - great, you can hold them to it and pursue further if it doesn't. If they say anything other than yes I would insist on the problem being correctly diagnosed first, and if they aren't able to do that then have someone else do it and then go back to them and demand they reimburse you.

Thanks Mark,

Good advice again. I've got everything ready and will be keeping my fingers crossed. If they do change the exhaust then I've got to go to Leatherhead on Friday to a funeral which will be a good test. 

Thanks again,

Alan

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Well today didn't go quite as well as I'd hoped. Got the car into Bristol by 10.00 am but was given a courtesy car as it would take so long to do the work! I had hoped to be there and actually watch the work being done. There were no unusual or suspicious forms to sign which was a relief and they were very kind and pleasant to me.  Around 4.00 pm I got a call saying they'd got the wrong exhaust parts and so couldn't complete the job. I've been back in and collected her do we can go to Leatherhead in our own car. Bit of a waste of our day but at least going in the right direction.

The only good thing to have come out of all this is that I've now driven yet another Lexus that pulled away smoothly and sweetly and there were no exhaust noises to be concerned about. This was the NX300 and whoever buys that one will be getting a good car.

Alan

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Hello, I saw the OP problem and got thinking.

I drive an RX400 h and I find even though I’ve had the car for 6 years it’s pretty impossible to know when the petrol engine comes in unless you are looking at the energy monitor whilst driving.

I haven’t driven for 450 new shape but I’m assuming that the technology has progressed from the 400 so you’d expect a smooth transition on par with my RX 400 ,

but the only time I can tell the engine is coming in is when i blip the throttle to accelerate and then there is a noticeable step or a jerk for want of a better expression, but this is normal...

I wonder if the initial jerk is what you are picking up on.


Sent from my iPad using Tapatalk

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19 hours ago, ISJason said:

I wonder if the initial jerk is what you are picking up on.


Sent from my iPad using Tapatalk

No, it's not the jerk that's my problem. I've just driven over 200 miles with just the rear part of the exhaust system replaced but not the centre section (as they got the wrong parts). I don't know whether I'm pleased or horrified as the problem is markedly worse. My wife drove home and said the same thing. Much, much more vibration coming up through but all they did was replace the end bit. How could that alone have made so much difference ? I was surprised to learn that they'd changed the centre section design at all so all I can hope is that when they replace that it will all be fine. Some hope !

Alan

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20 hours ago, stringbender said:

I don't know whether I'm pleased or horrified as the problem is markedly worse.

That's a good thing for two reasons. It will be easier to prove the issue to them and as they made it worse they're now fully on the hook for fixing it.

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2 hours ago, m4rkw said:

That's a good thing for two reasons. It will be easier to prove the issue to them and as they made it worse they're now fully on the hook for fixing it.

I've had a look underneath and can see the new end pipe. What's interesting is that they put 2 new rubber hangers on for the new silencer (they're just on the engine side of the large silencer ) and these are different to the original ones. For some reason Lexus has changed the rubber from 18 mm thick to 28 mm thick. I've said all along that these two hangers are at 90 degrees to the other 4. There was barely any room for movement on the old ones and now there's practically none. If Lexus has changed the centre section for some reason then they may also have redesigned the bracket that bolts to the underside of the body that the hangers are fixed to.

Seems a daft idea to me to have 4 hangers that allow maximum movement back to front but then fit the remaining 2 hangers to prevent this movement. So how come every other 4th gen. RX has no problem ?

Alan

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