Have owned my 2004 Touareg 2.5 TDi from new, currently has 159k on the clock. At around eighty thousand miles it occasionally went into limp mode and then for months after would be fine. At around 90K the engine shut down completely whilst on the motoway and refused to restart. After recovery the ECU was diagnosed as being faulty and was sent off to be refurbished. All has been well until recently when the engine went into uncontrollable "race mode" with clouds of white smoke, leaking injector seals had filled the sump with diesel. Thereafter the problem with limp mode returned with an overboost error P0234, and with the ability of only able to travel a few miles without having to switch off and restart the engine. The turbo was diagnosed as the issue and subsequently replaced. Whilst replacing the turbo has been a major inprovement, general driving on town and country roads is without issue but on an open road or motorway, particually with a slight hill, on opening the throttle up the engine goes into limp mode, managing only 38 miles mile per hour. Hoses have been checked the EGR valve replaced as well as the boost pressure sensor. Can anyone please offer some advice on what action to take next? 😪
Thank you for posting this.
I also have a 2004 R5 and have EXACTLY the same problem/symptoms. Mine has 159,500KMs (appx 99k miles)
This all recently started when I noticed that if I push the pedal to the metal a little more than usual (say 3k RPM +), the dipstick would pop out and oil would start coming out, and I read all kinds of horrifying stories about compression valves, engine failures looming etc, so decided to change the PCV valve first as that's very cheap and very easy to change (sits on top of the engine and comes out by hand). That did not do anything so then I put my VCDS and it gave me an over-boost error below. (VCDS is worth its weight in gold).
Driving around town under 2000RPM cars runs like a swiss watch, so quiet I can barely hear the engine (surprisingly quiet for a diesel). As soon as I pop on the motorway and go to 2,500RPM +, the car goes into limp mode until I pull off and restart the engine, after that its fine again. My garage at home has a steep incline when exiting and the car struggles to get up it, showing 99.9L/100km so I understand this is an indication that the engine is pushing more diesel to the engine than normal (so possibly some kind of sensor issue) as usually ut would show 65-70L/100km.
So thanks for posting this as I thought I was the only one and hopefully some of the comments will be ale to help me.