Had this happen several times now, where I am booting it to get up to speed or starting an overtake and the engine just goes flat, no boost, and revs in each gear pegged to maintain the current speed but not allow any increase, even with the pedal in the carpet. Could this be the EGR system (blocked pipe, stuck valve), turbo wastegate (if it has one) or something else. The CEL doesn't illuminate, and switching the engine off seems to reset it it, but if you try to keep driving without restarting then boost/revs stay capped, making the car awkward to drive.

Thanks in advance for any help and advice.

Oh, and it's a 2006 2.0 TDI PD140 Ambiente 6sp.

you really need a scan with vcds. could be any number of things. check out the owners map.

Sounds like its going into limp mode, I believe I have read that it can do this under certain circumstances without putting the CEL on.

As above get it scanned for fault codes.

I had this exact problem before my turbocharger gone away.. but as said, there could be a lot of reason for this..

How did I know 'it could be any number of things' ? Because it's a bloody VW !!!! The sooner I'm rid of these cars the better, sick of all the constant unreliability and expense. If I go to the dealers they'll want £90 to just tell me what's wrong, but it is due to go in for a service where they'll have it plugged in anyway, so maybe they'll diagnose without further charge. Please let it be a minor niggle, I simply can't afford another VAG raping of my bank account :(

My get went on my old Alfa 156 jtd. Had exactly the same symptoms. Would be the first place I checked.

I had a problem like this on a passat 1,9tdi. It turned out to be a small hole in a rubber air hose before the turbo, causing it to take in excess air and leading the engine management system to limit engine revs. A simple hose replacement sorted it. One of the lower cost solutions to consider first of all.

Yeah, gonna have a good rummage about looking at all hoses and stuff, maybe pop the EGR tube off and give it a clean out.

My money is on the vanes in the turbo sticking causing an overboost condition. Get a local member with VCDS to scan the car for you to get the fault code then you can start troubleshooting.

How did I know 'it could be any number of things' ? Because it's a bloody VW !!!! The sooner I'm rid of these cars the better, sick of all the constant unreliability and expense. If I go to the dealers they'll want £90 to just tell me what's wrong, but it is due to go in for a service where they'll have it plugged in anyway, so maybe they'll diagnose without further charge. Please let it be a minor niggle, I simply can't afford another VAG raping of my bank account :(

Iv said to people in past a few times when they have slated VAG's..You name me one car ever to be produced that has 100% reliable..you cant because there is'nt one. All cars go wrong, looked after or not, thats mechanical engineering for you!

What you need to do if you have a troublesome car is either A, find yourself a good VAG specialist (dealership is only ever good if your daft in the head or have FSSH) or B, Get rid in hope of buying a completely reliable car, good luck with that

I guess I was spoilt with my previous car. 3 years, 60k miles, 23 trackdays, driven like my hair was on fire every day and the only issues were an O2 sensor (fixed free under warranty) and an EGT sensor (£60). I had a VW Corrado for 13 years and that car never passed a single MOT, never had less than 5 concurrent faults and cost me a fortune to keep on the road. Since returning to VAG ownership with our two Skoda's I have had problem after problem, and since the warranty ran out the expense and hassle has strained my patience. Our Subaru was brilliant, in every way not just reliability, as was the Honda, but the five VAG cars we have had have all been reliability and financial disasters, and it isn't just me. I have several friends and family members with them and they all experience similar tales of woe. When I visit the Subaru forums it's usually full of people asking how to make their car even better, or how to fix something they've knackered themselves in some attempt at modifying, but on here it's just a constant stream of 'what's wrong now' ! VAG cars are great from new, with the warranty in place, but once wear and tear kick in and the safety net expires, GET RID QUICK !!!

I had a few costly problems with my Octavia vrs when I got it. I bought it from an independant garage. My main dealer has sorted it all out now, last service didn't result in any unexpected costs and it sailed through the MOT.

I don't drive it around at 7000rpm all the time, don't do my 0-60 in 7 seconds from the traffic lights... I look after it and I get no problems....

Next octavia vrs I get (yes I to realllyyyyy love my vrs, completely hooked) will be from a main dealer, and it will be petrol again =)

I've got a service plan on it now which spreads the cost of servicing and have warranty direct cover - complete peace of mind.

Many thanks to MattP for running a diagnostic this morning. Came back with...

Cyl 2 Glowplug circuit (Q11) P0674 Electrical Fault

Cyl 4 Glowplug circuit (Q13) P0674 Electrical Fault

Boost Pressure Regulation P0234 Limit Exceeded (Overboost Condition)

So, I guess I need two glowplugs (unless their fault is caused by the boost issue) and a boost regulator ?

Hmm, five minutes of Googling and my head is spinning. Could be the boost regulator, or its loom, but also could be everything from the turbo, to the vanes, to the EGR, to the MAF sensor, MAP sensor and God knows what else.

GRRRRRR !!!!!!!

Almost certainly it'll be the turbo vanes sticking, so its either new turbo time or try cleaning your existing one to free the vanes off.

It'll have to be a clean up as I simply cannot afford a new turbo. Christ, even with the 18mpg fuel economy my Subaru was MASSIVELY cheaper to run than this bloody thing, and LOADS more fun.

Doing some further research it appears the vanes in the turbo have a habit of clogging up with carbon, the vacuum actuator can fail, or the solenoid for that, the N75 sensor, related piping and vacuum lines, the EGR and its related piping, the loom to all the associated electronics, or the whole bloody turbo. Two glowplugs showed faults too, and they could either be the plugs themselves, or the wiring which has a habit of failing too.

Gonna try a basic de-coke by running high revs under load for 20 minutes or so and see if things improve, then speak to some turbo specialists.

Well, looks like it was carbon clogging up the vanes. On a trip to the Lake District there was a very long hill I climbed several times and took the opportunity to do it in a lower gear than normal so the revs were high. The extra heat through the turbo seems to have de-coked it as it hasn't gone into limp mode since.

If you want to experience financial free fall, then you might want to consider buying something with a blue oval badge....believe me, that is painful.