Hi all,

I'll preface this with the fact I'm not technical but I try to do a few basic bits here and there... so please forgive my lack of knowledge but any advice would be much appreciated.

Over the last few days I have begun to experience a drop off and then pick up in revs (like I'm tapping my foot on and off the accelerator) between 1500 and 2000rpm, normally when I'm only just touching the throttle. This can be going as slow as 30mph, or at 70mph. It only occurs when the engine is hot after a good 45mns driving. No codes are logged (I have a basic code reader).

Some Googling suggested either the Crank Position Sensor or a split intercooler hose.

I replaced the hoses 6 months ago after a split, so looked to the CPS. I replaced that yesterday, but experienced exactly the same issue on a long drive today. However, shortly after the issue started today I had to accelerate hard as I was on an incline. There was a loud bang and immediately it went into reduced performance mode.

Got home and looked under the bonnet and the top intercooler hose had blown off. The RAC attended and refitted it but it blew off again when accelerating hard on a quick test drive. Logged P006A.

RAC guy says that it could just be that the inside of the pipe is now slick with oil residue and that basically it will just keep popping off no matter how hard he clamps it down and needs replacing, ideally with silicone. He also mentioned the possibility of a blocked intercooler or overboost.

So my question is, do we think that maybe I didn't fit it that well 6 months ago and it just reached a point that when it is hot and more supple it was leaking a little around the jubilee clip causing the rev issues and that it just let go today... or does it sound more sinister?

Any advice would be much appreciated.

Thank you in advance!

**UPDATE** When I replaced the intercooler hoses 6 months ago, the kit came with a new rigid plastic pipe section, which I used.

Upon inspection, the original (which I had kept) had steel collars where the hoses were clamped on whereas the new one was just plastic. I had suspected that the plastic was becoming supple when hot and was breaking the seal and letting air in, thereby causing the dipping and surging, and also making it easy for the hose to blow off; so the hard plastic element was swapped out for the original.

However, I'm still finding that after I've been driving for a longish period of time (say and hour), I will start to experience exactly the same issue of a drop off and then pick up in revs (like I'm tapping my foot on and off the accelerator) between 1500 and 2000rpm, normally when I'm only just touching the throttle.

I now have no idea what might be causing this... it never happens when the engine is cold, only after a period of driving.

The garage can never experience it so I'm now completely stumped!!!!

Any ideas would be much appreciated.

Is the fuel filter an OE or genuine LR item. Aftermarket filters can cause issues when it's hot. 2009 Rimini Red SE TD4. Soon to be sold.
Hyundai Ionic 5 Ultimate on order.
Gone. 2006 Tonga Green i6 HSE.

Hi Nodge68

To be honest, I'm not sure. The filter was changed about 9 months ago, but I didn't do it so wouldn't know if it was a genuine part (I'd hazard a guess not). I didn't realise the filter could cause issues when hot so perhaps I'll change it.

The strange thing is, it's been driving fine and this all just started one day out of the blue.

There is an issue where some aftermarket filters don't have the fuel temperature control thermostat in them, allowing hot fuel to recirculate to the HP pump, instead of drawing cool fresh fuel from the tank on hot days. The hot fuel returned to the HP pump upsets the ECM, putting the engine into a lower power safety state, to protect the HP fuel system.
This normal results in loss of power, but could cause other symptoms too. 2009 Rimini Red SE TD4. Soon to be sold.
Hyundai Ionic 5 Ultimate on order.
Gone. 2006 Tonga Green i6 HSE.

Hi all, things have moved along with this so I have started a new post here:

https://www.freel2.com/forum/post437308.html#437308