I was returning home a couple of days ago and as I approached the house the car surged ahead. I had to brake hard to stop it. I pulled slowly onto the drive and the engine surged in speed to full revs with clouds of smoke coming from the exhaust and under the car. I quickly turned off the engine which fortunately stopped. There were no engine warning lights and subsequently I checked the codes. There were no error codes except one to say the engine had over revved. I checked the oil and the level was normal. This has happened to me before about 50k miles ago and I had to replace the engine. In that case the fault lights lit up with numerous error codes. I cannot believe this has happened again. About 5K miles ago the DPF was cleaned and an EGR valve replaced. Since then there have been no engine associated error codes. I carefully check the oil level often as I am nervous after the first failure. I would be grateful if anyone could suggest what might have happened. Thank you.

Well, the first thing that I would check is if the driver's floor mat as wedged itself against the accelerator pedal which is a common feature with the Jaguar XJ8's.

Thank you, I had forgotten about this cause, but alas no!

Try a hard reboot as it certainly wouldn't hurt, and check the earth grounds inside the boot.

Have you noticed an increase in (lube) oil consumption? In some diesels, worn rings can lead to the engine consuming lube oil in place of fuel, which will make the engine "run away" as the normal fuel-control mechanisms cannot regulate the 'fuel' available to burn. Older Detroit Diesels were famous for this condition, but I have seen it in 'high service hours' four-stroke diesels as well, and it can be scary!

I have tried the reboot as suggested by Rickkk and have re-done the earth points. The engine runs slightly smoother at tickeover, but if you increase the speed above about half revs the speed takes off again and I get clouds of blue smoke from under the hood. Strangely still no error codes. Before this there was no evidence of piston ring wear. The car has just had an MOT and the emissions were extremely low to the extent that the testers commented on it.

The oil control rings could have a wear problem, or failure, that hasn't affected the compression rings yet.......... Just an observation; Good Luck

Have had this happen quite a few times on different engines have found that the engine idles fine then when your raise the revs it picks up and overspeeds and it turned out the bearings on the turbo had started to go allowing oil past the seals dont start the engine if auto as it can runaway and kill it self check the turbo look in the intercooler and pipes for oil make sure first if not then it will be rings or valve seals but firt check the turbo they dont really startto work until revs get to about 2000 rpm hope this helps remember do not start until you are sure you have checked good luck hope this helps

+1
The phenomenon is called "diesel runaway". The engine runs on the engine oil until it's all gone then siezes.

Yes a couple down the road from me had this happen the chaps wife pulled up in the drive in a cloud of smoke it would not stop she had turned it off and removed the keys she did not know what to do so she went indoors and closed the door 20 mins later it stopped engine totaled that was an auto if its manual you can put it in gear and foot on brake dump the clutch to stop it better a new clutch than an engine

Thank you for all the replies. It is starting to make sense. The car goes in on Thursday to be looked at. I'll post the 'end story'.

You may be on to it, Roadsider. We don't get the diesel variants here in North America, and I didn't realize they were turbos. That line of thinking would explain why the problem only shows up at higher rpm (when the turbo spools up), and might not have been flagged or spotted during the recent MOT test.

Fuel diluting the engine oil and causing level to rise.Then it runs away, change oil. If you dont do many miles sell and buy a petrol.