Recently took the car in specifically for this problem. Previously looked at during two other scheduled services. Upon initial start of the car where: the car is turned on, there is a pause as the car initializes and finally the engine will start up. It is at this point where the engine stumbles badly. Sometimes it is very rough and there is some "clacking" noise coming I think from the engine bay. The car will stumble and proceed running rough as I drive away. The car will stumble upon moderate acceleration. At times during other parts of the day, the issue is less pronounced however the engine seems to miss while idling or slow maneuvers from a parking spot. Also, at normal operating temperatures, the engine does not turn off at a stop which I believe happens normally with the hybrid. Other times it does turn off. These symptoms will disappear and then reoccur without any clear common denominator.

Dealer again ran diagnostics without any revelations. They also contacted Lexus corporate offices for any additional information. No definitive cause only to say that it seems to be a fuel issue. I've only used top-tier premium grade fuel. Prior to bringing the car to service I ran two tanks of Chevron Techron fuel system cleaner to see if I could clear the situation up. Not so and therefore I took the car in for service.

I am try to stay with one brand of gas to see if I can narrow down any fuel problem but the stumbling continues.

Any comments on similar experiences is appreciated.

 

UPDATE: Luckily I noted how many times I've asked to have this issue looked at by my dealer. During my last service, they again included Lexus in the testing. The car was kept a couple extra days for tests. Nothing was found to be "broken" but Lexus approved to have all the injectors replaced under warranty. After a couple weeks I can say that the issue was resolved.

 

Did Lexus ever indicate what caused the injectors to need replacing? Were some of them defective?

 

No, they made sure to say that nothing was wrong with the car. I had run a couple bottles of Techron and a can of Royal Purple fuel system cleaner without getting this to clear up during this experience. The car just clocked 50K and I experienced this problem for about 30K miles.

Glad this looks to be resolved.

 

During this time that the car was running rough & then after the injectors were replaced, did you notice any difference in fuel mileage?

 

I

Dirty Injectors on removal

Ready to be fitted with new seals and insulators
I have a RX450h 2016(74K) which has the Atkinson cycle engine 3.5 litre . It has had a slight lumpyness on engine start for about 30 seconds then runs perfectly . I tried a couple of petrol cleaners but to no avail . yesterday I replaced the (port) fuel injectors and that has cured it .This engine has both port and direct injection .No fault codes were shown , but you could hear the misfire and it was logged in techstream . I wonder if this method would do a better job than the petrol additives . Engine valves etc were all clean on inspection down intakes but injectors slightly dirty . So if you have a 450h which you notice this synptom , I can give advice

 

Have you always used Top Tier gasoline?

 

I have only had the car a short while so do not know what the only other owner used , Most petrol in UK is E5 ...........I think its more to do with the driving habits of the RX hybrid in cities where it never gets a good "blow out" and is ticking over most of the time ..............

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This was the sound ..........first 10 seconds of video .............. quite concerning but now rectified by the injectors !

 

Yep, the misfire is clear in that audio, over the background (normal) clatter of the fuel injectors.

 

I can get my cars to clatter like that if I start it for just a few seconds, such as moving it into or out of the garage, and shut it off. The next time I start it, it sometimes will clatter, especially bad when the weather is cold. When it does happen in my RXh it will settle down pretty quickly. The RXh warms up incredibly fast. If I'm just moving the cars I try to let it run for 30 seconds or so and rev it ever so slightly to try to burn off as much as I can before shutting it off. We also have a plug in hybrid which runs the gas engine on and off constantly, much more so than a hybrid. It also clatters like that at times. I'm not saying this is what the OP is experiencing, but what I described above may be a contributing factor over time.

 

Yep that sounds like you have this issue ................. if you want to clean your injectors it will cure it !

 

What I described above is not unique to my RXh or Lexus in general. If I start a cold car and run it for just a few seconds and shut it off, the next time I start it, it will usually start rough especially in the cold. I've always thought it's from unburned fuel. I know it's not a good thing to do but sometimes can't be helped. This is why I wish Lexus would let me force on EV mode when the car is cold. I think I brought this up on another thread before. Lexus hybrids with a 4 cylinder engine, forcing EV mode is a lot less restrictive than the V6 hybrids. To be clear, my RXh always starts smooth if the previous drive was a normal drive.

 

We had multiple "chatter" noise posts in TCH forum at TN. No one really figured what and why but, we sort of leaned towards lack of oil pressure to tighten timing chain and bring valvetrain in proper working order. What andye describes, we had several owners confirming same. If you really think about it, you are moving oil starved engine.
Unless you have high pressure injectors, like on NXt, injectors should not be making any noises. Even NXt I owned, that was not really an issue. But we had TCH engines plagued with excessive oil consumption and low oil pressure issues. Just saying. Same issues tend to spread across same manufacturer various models and engines, as many parts are cross-used and philosophy of design and manufacturing is same.
Injectors in picture above appear to be covered in soot. What points towards incomplete petrol mix burn. I don't know, how much of it sticks out into combustion chamber, if it's only the nozzle tip, then there is oil leak onto injectors body. If it's soot, question is - why there is incomplete fuel burn? And, with cause no fixed, how soon same problem will return?

 

You raise a few points here ................... but all i can tell owners is what my experience is . I have been working on cars and bikes since i was 14 and i am just going on 70 and I am a qualified engineer in both mechanical and electronic fields , so I am no numpty when it comes to diagnosis . ...... which doesn't help when you have to launch yourself into the engine bay horizontally to get at the rear bank of the v6 LOL.
The inlet manifolds are kept reasonably clean with the port injectors at start up as I can vouch for . I had a good look when I removed the fuel rail . What is happening is the injectors are in a recess out of the main flow and over a period of time will build up carbon as they are basically not cleaning themselves , only the ports and backs of the valves . I think that the engine in recharge mode at standstill is set to run slightly rich at start akin to the old choke so the carbon on the inlet is not excessive . I think that because the atkinson hybrid setup that idles a lot at standstill to charge the HV etc is why it looks like there is incomplete burn . I think that those who drive the car hard will not suffer as much from this symptom .I put this post up so that those who experience that clacking on engine start that sounds as if there is a big mechanical problem are reassured that its only the layshaft in the power split transmission clanking as its not getting an even drive from the engine input shaft. Also if you put Techstream in monitor mode you can see the odd misfire on start up with the car stationary. This is NOT enough to trip a code but enough for the human ear to pick up the lumpy running . By the way , all this goes away after 20-30 seconds . I expect that this is because she then goes to direct jinectors instead of the port injectors or maybe a combo of both depending on what the ECU sees. Possibly this is why people think it may be camshaft timing related .
As regards the vvti oil pressure etc . this may have been a problem on pre 4th generation , but the cams on the 2GR FXS engine are electrically controlled as there are 4 motors on the camshaft sprockets . , so the non locking pawl and various other problems that occurred on the early IS250 engine etc are not relevant to the FXS engine .
I think that this problem should be highlighted by the mods by making it a sticky to reassure owners that this is not a terminal clacking of the drivetrain !!

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"Injectors in picture above appear to be covered in soot. What points towards incomplete petrol mix burn. I don't know, how much of it sticks out into combustion chamber, if it's only the nozzle tip, then there is oil leak onto injectors body. If it's soot, question is - why there is incomplete fuel burn? And, with cause no fixed, how soon same problem will return?"

Just re read your post !
The injectors I am talking about are PORT injectors ...not the direct injectors that are in the combustion chambers . This engine has 16 injectors 8 Direct and 8 Port ( intake ). the port injectors are behind the intake valves in the intake after the plenum chamber The reason for the 2 sets is that the port injectors were reintroduced to keep the intake valves clear of gunk which became a problem when manufacturers changed to direct injection alone from the original port type injection .
So in conclusion both sets perform a combined function to be efficient and clean at the same time