Have you had fuel pump tested to make sure pressure ok

When was the last time the Diesel fuel filter was serviced?

Bummer you've had no replies - I have a 2017 CRDI myself - oil levels seem ok, I always use top quality C3 rated oil - change at 10k intervals or so.

I can't assist with the ECU info etc - but personally I find the Hyundai management of active DPF activation incredibly poor & makes things worse for drivers. The model I have (1st gen PD) gives no indication at all to the driver of the DPF's status nor when the ECU initiates an active DPF burn.  Yes, folks will tell you that you can sometimes tell when this is or has been - but it's often hard to pickup on - hence the driver will often turn the car off when it's midway through this, making it worse.

I've no idea why Hyundai couldn't have done what every DPF fitted car I'm aware of does, which is to have an icon on the dash to SHOW to the driver when it's doing an active DPF clean - these vehicles will generally tell the drivers in the manual to allow the car to continue to run until this light goes off.

But no, Hyundai did nothing like this - so it's really a guessing game. Very poor - and beyond this I'm really unsure why there couldn't be an easy way through the menu to see a simplification of how the DPF is doing - hence you could decide to do a long highway trip etc - just to clean it out.  Again Hyundai in their wisdom chose not to do this - go figure.

Thanks, that's a fair comment about the thinning, and not one I'd thought of (obviously 🤦🏻‍♀️).
As for the fan - I've not heard it kick in and my dashboard temp reading is always within limits, so maybe I can rule that bit out?.
The air con needs regassing - has done for at least a couple of years 🙈 - and I've put it off as I've been told it's the dearer type it needs (tbh, I've forgotten which type it is, it's been that long). I've not pursued it as I don't mind cracking the windows open instead of using that, but if it would help with the bunny hopping, maybe I should think about getting it done? (Let's be honest here, it not looking like I'll need to do it due to the weather, anytime soon, is it?!? 😄)

Hi everyone, please bear with me...this is my first post.

My 2012 CRDi blue drive active has taken to bunny hopping when temperatures get to around 18°C (& above).
It starts up ok in all weathers and doesn't do this in cold/cool weather, just when the mercury starts to rise.
There's no particular speed at which it gets worse/better, and causes a bit of drag on the acceleration/drive, but then seems to settle down after a few minutes (maybe 5?)
It's as if fuel is struggling to get through, but I can't understand this as I thought fuel got thinner in warmer weather and therefore flows easier (please correct me if I'm wrong...and if this is indeed the problem I have 🙈).
It's frustrating, but also concerning as I work 15 miles from home, travelling on one the regions busiest motorways.

Has this happened to anyone else, or can anyone shed some light on what it might be?

Thanks