Engine running rough at low revs / speed

[Chris Owen]

Following its last service my UX F Sport (2023 model) engine runs rough as you pull away but only for 1/2 to 1 second. (It is accompanied by a very small vibration). The engine can also be heard to run rough when stationary if revved ever so slightly but again only for 1/2 to 1 second. I can not maintain the rough running.

When in electric mode this doesn’t happen.

I have contacted the service centre / dealer and await their reply but if anyone else has experienced this please post.

Cheers Chris

[Don C]

Most unusual for a UX Christopher.  Look under the bonnet to make sure there are no pipes off.  There isn’t much else to go wrong.  

[Chris Owen]

I’ve done a little more investigation this evening. (with the car stationary in park) I found the engine vibrates / feels rough between 1200 and 1400 rpm. Above and below this and it runs smooth.

There’s nothing obvious out of place under the bonnet.

[Don C]

2 hours ago, Chris Owen said:

I’ve done a little more investigation this evening. (with the car stationary in park) I found the engine vibrates / feels rough between 1200 and 1400 rpm. Above and below this and it runs smooth.

There’s nothing obvious out of place under the bonnet.

It seems odd that it’s only since the service.  I’d need it on a lift to look underneath.  Have you pulled the top cover off?  It literally pulls directly upwards.  

[Chris Owen]

I’ve had the cover off and everything is connected as expected. I’d delve further but seen as it’s under warranty, I’ll leave it for Lexus to sort. (I’ve an original defender requiring new discs, callipers and pads to keep me busy at the weekend).

I did wonder whether during the service there was an engine software update? (It was a full service).

[Andywhy]

Did this amount to anything? I also have a similar rattle but not rough running. I'm suspecting it's a heatshield rattle but I haven't confirmed yet. The dealer won't help me any further with this as they say they have exhausted all options.

[Chris Owen]

It’s booked in on the 13th with the dealer, (I’ll post the result). It is however getting worse, it happens over a slightly larger rev range but again only at lower revs.

[Andywhy]

Test this going up a steep-ish gradient and holding the throttle around those areas. That's how I replicate it on mine. Usually within the lower to mid portion of the power meter.

My last car was torn apart looking for this to no avail. I got another one and this has also started doing it which is frustrating, so I'd like to get to the bottom of it. I think it might be the heatshield in the engine bay directly behind the firewall as I have adjusted it once and it seemed to stop it for a while. I also find it happens more when it's warmer weather.

Could you keep me up to date on what the dealer finds if you wouldn't mind? I'm hoping one of us finds a solution to this if it's the same rattle.