Shuddering or Lumpy running

Ian 101 · August 3

I have bought a 2020 Lexus 250UXh a few months ago. It has less than 40,000 miles on the clock and it has been serviced by Lexus from new.

The car has an intermittent fault. The engine feels like it is shuddering and the engine runs lumpy. It can feel like you are driving over a bumpy road surface or rumble strips when the road surface is smooth. It can also feel like it is misfiring. Passengers have noticed it and commented.

The fault happens in the following situations: -

When you turn the ignition on, engine cold and the car is stationary

When accelerating gently at lower speeds around 30 mph

When decelerating at lower speeds around 30 mph

I reported the fault to Lexus before the recent service on 5th April 2024. They plugged it in but could find nothing on the diagnostics. They suggested that I avoid supermarket fuel and only used a premium brand, which I have done since then. However the fault has continued.

Has anyone experienced anything similar and if so were you able to find a solution?

NemesisUK · August 3

I had similar in both my RC, always around 1500rpm. No faults found and just ignored it. A very transient thing felt through the steering wheel and footrest...

ColinBarber · August 3

11 minutes ago, NemesisUK said:

I had similar in both my RC, always around 1500rpm. No faults found and just ignored it. A very transient thing felt through the steering wheel and footrest...

That sounds like the resonance issue the IS300h also suffered from but seems different to what the OP is experiencing. For what it's worth, my wife's 2020 UX250h doesn't have the symptoms Ian is describing (and she rarely uses anything other than supermarket fuel).

Assuming it is engine, but not severe enough to trigger a fault, then I'd start by using a quality fuel injector cleaner to see if that helps.

wharfhouse · August 3

1 hour ago, Ian 101 said:

I have bought a 2020 Lexus 250UXh a few months ago. It has less than 40,000 miles on the clock and it has been serviced by Lexus from new.

The car has an intermittent fault. The engine feels like it is shuddering and the engine runs lumpy. It can feel like you are driving over a bumpy road surface or rumble strips when the road surface is smooth. It can also feel like it is misfiring. Passengers have noticed it and commented.

The fault happens in the following situations: -

When you turn the ignition on, engine cold and the car is stationary

When accelerating gently at lower speeds around 30 mph

When decelerating at lower speeds around 30 mph

I reported the fault to Lexus before the recent service on 5th April 2024. They plugged it in but could find nothing on the diagnostics. They suggested that I avoid supermarket fuel and only used a premium brand, which I have done since then. However the fault has continued.

Has anyone experienced anything similar and if so were you able to find a solution?

If you can replicate the issue on demand then take one of the Lexus service techs out with you and show them what's happening - I've generally found that's the best way to get to the root of these sort of problems a few times over the years (with whatever car I was driving).

Ian 101 · August 3

Thanks for your response.

Did you find a way to minimise the effect or have you just accepted the issue and have learned to live with it?

PRT68 · August 3

Surely this has to be a faulty plug or coil pack. I had exactly the same symptoms in Prius, and it was a plug. Genuine Toyota plug that failed after 20,000 miles. Don't know which one it was as I changed all 4. Couldn't be bothered to faff about, and that sorted it.

If that hadn't worked, I would have bought a new coil pack and swapped it about until cured.

Ian 101 · August 4

Thanks for the responses. I think my next move is to record each incident and then arrange for a Lexus technician to accompany me on a test drive to try and replicate the issue.

Charli Alder · August 4

Hello Ian. When I had my 17 plate CT a lot of owners reported a similar problem on LOC that was due to the EGR being Gummer up and needed thorough cleaning. Not sure the same applies to the UX engine. BTW I have a UX250H 70 plate and only use Esso E10 fuel or equal but every now and then some E5.

Please let us know the outcome of your problem.1

Don C · August 5

Can you get somebody to record it while you drive. I’m of the opinion that a set of plugs are worth trying at 40k like Paul above. They aren’t due until 60k but they are known to play up and in any case, it isn’t a bad idea as it’s a serviceable item and easy to do. It takes them out of the equation. I do agree that avoiding supermarket fuel is a good idea despite the hecklers. It is devoid of additives that help the engine run well.

RONNIE W HODGEKINSON · August 5

On 8/3/2024 at 1:31 PM, wharfhouse said:

If you can replicate the issue on demand then take one of the Lexus service techs out with you and show them what's happening - I've generally found that's the best way to get to the root of these sort of problems a few times over the years (with whatever car I was driving).

Good Advice Phil..Have taken this on Board Myself..!!!!

Ian 101 · August 21

HI

I followed your advice Phil, arranged for the car to go in to Lexus and asked for a technician to test drive it with us in the car. More than slightly worried as the fault was intermittent and may not occur on demand. However within minutes the very knowledgeable technician identified the fault, he suspected that it was a fuel injector. They checked the injectors and found that it was Injector No 2, which Lexus replaced under the Relax Warranty. The car is now driving smoother than ever. Colin, you were correct with your suggestion regarding the fuel injector. "Result!"

wharfhouse · August 21

8 minutes ago, Ian 101 said:

HI

I followed your advice Phil, arranged for the car to go in to Lexus and asked for a technician to test drive it with us in the car. More than slightly worried as the fault was intermittent and may not occur on demand. However within minutes the very knowledgeable technician identified the fault, he suspected that it was a fuel injector. They checked the injectors and found that it was Injector No 2, which Lexus replaced under the Relax Warranty. The car is now driving smoother than ever. Colin, you were correct with your suggestion regarding the fuel injector. "Result!"

That's a great result - persistence paid off. Any car can have a random fault - fortunately Lexus seem to have less than other marques but all the same there are bound to be odd ones and good that it was all done under the Relax warranty.

Don C · August 21

I’ll get shot down in flames for saying this but supermarkets are not your friends. The fuel is cheap because it lacks the additives that prevent injectors sticking and valves carboning up.

Here we go….. I’ve been using supermarket fuel for 400 years…….….. ……..well you might have been but not in a car with a Euro 6 engine.

Lmafudd · August 22

16 hours ago, Don C said:

I’ll get shot down in flames for saying this but supermarkets are not your friends. The fuel is cheap because it lacks the additives that prevent injectors sticking and valves carboning up.

Here we go….. I’ve been using supermarket fuel for 400 years…….….. ……..well you might have been but not in a car with a Euro 6 engine.

I hate to disappoint Don. I've been using supermarket fuel for years, though not 400. Never had an issue. I once did a two month test putting the more expensive version in the NX and didn't see any mpg improvement. I didn't do it to improve the running as there wasn't a problem to cure. I'm not disagreeing but just relaying my own experience.

A service engineer once told me that modern engines have some self adjustment and the worst thing is to keep swapping and changing fuel grades. Not sure that's true but seems to work for me.

Tel · August 22

I use Supermarket E5 fuel.

Gives super smooth performance.

Tel

Don C · August 24

On 8/22/2024 at 6:11 AM, Lmafudd said:

I hate to disappoint Don. I've been using supermarket fuel for years, though not 400. Never had an issue. I once did a two month test putting the more expensive version in the NX and didn't see any mpg improvement. I didn't do it to improve the running as there wasn't a problem to cure. I'm not disagreeing but just relaying my own experience.

A service engineer once told me that modern engines have some self adjustment and the worst thing is to keep swapping and changing fuel grades. Not sure that's true but seems to work for me.

Not in an E6 engine you haven’t. The test shouldn’t be for fuel consumption, it is the long term benefit in injector operation and the EGR and GPF. Use what you want, it doesn’t matter to anyone else.

Srishail Kumar · August 25

On 8/21/2024 at 11:40 AM, Ian 101 said:

HI

I followed your advice Phil, arranged for the car to go in to Lexus and asked for a technician to test drive it with us in the car. More than slightly worried as the fault was intermittent and may not occur on demand. However within minutes the very knowledgeable technician identified the fault, he suspected that it was a fuel injector. They checked the injectors and found that it was Injector No 2, which Lexus replaced under the Relax Warranty. The car is now driving smoother than ever. Colin, you were correct with your suggestion regarding the fuel injector. "Result!"

Hello Ian - Thank you for the update. Was the repair covered under warranty? I fear there’s a similar issue in my 2020 UX.

Tel · August 26

Don,

You do not keep your cars long enough to confirm the so-called added benefits of non Super Market fuel-----as you say it is a very personal matter .

Any idea what the LBX engine is on the Euro Scale & both my Local Toyota & Lexus Dealers say they use Factory oil viscosities.

I will believe them when I get my Free 1st. Service next year.

Terry

Don C · August 26

12 hours ago, Tel said:

Don,

You do not keep your cars long enough to confirm the so-called added benefits of non Super Market fuel-----as you say it is a very personal matter .

Any idea what the LBX engine is on the Euro Scale & both my Local Toyota & Lexus Dealers say they use Factory oil viscosities.

I will believe them when I get my Free 1st. Service next year.

Terry

Harsh but true.

They easily exceed Euro 6 and they use 0W/8. I can tell the difference in running high octane in smoothing out the engine but you are right, my obsession in changing oil and benefitting from the additives in fuel are seldom realised. Occasionally a friend who buys one of mine does.

LexusUX250h · October 9

Good afternoon,

I have a similar issue with my UX. Car holds back when accelerating/pulling away from standing still. Last for about 2 seconds but can and has created dangerous situations when merging or crossing a road.

I called Lexus Chester when I was in the UK and the mechanic I spoke to recognised the symptom. They recently replaced the injector (nr.2) for a customer. Can’t tell for sure if this is the exact same issue but the fact they recognise the symptom straight away says enough.

Since I live abroad I had to contact my local dealer. This is where the issue is now being investigated. My suggestion to contact Lexus Chester is being ignored by the TD of Lexus. Maybe afraid of having to do a recall ?