TDI turbo entering limp mode

[pandj]

Hi, we are new to the forum and are pleased to have found it.

Our 2002 Octavia TDi 110 Elegance has developed a few non-permanent problems, particularly with the turbo, or so it would seem. I will try to give a clear description.

When the engine is cold and if accelerating only slightly more than a steady increase in speed say no higher than 1750 - 2000 rpm, we feel a series of fall and rises in performance in rapid succession, accompanied by a wheezing sound, so we back off the use of the throttle for a moment. This can be encountered within the first 0.5 mile on a slight downhill run, and then moving away from a junction. As the journey time increases and the engine warms up all seems to be ok. Maybe after about 7 or 8 miles when driving up a long hill/dual carriageway, the engine enters "limp mode" with throttle down at about 65-70mph. So I stop, switch off and start up again after a few seconds, and driving is ok for the remainder of the day. If I don't stop, the car lacks power and very slowly builds up speed. I did decide to change all air and fuel filters when I found two were clogged even though it was supposed to have been serviced by a main agent. That made a noticable difference. Could oil lines to the turbo be clogged and need replacing? Any further suggestions please.

I have also just noticed that the temperature gauge is rising and falling, and it sometimes drops back to zero when on the move. The coolant sensor unit seems to be easy to replace, but just need to make sure it's the right one. Could these two issues be related?

Thanks in anticipation of your help.

[mbames]

My car (2001 TDi110) does some very similar things. When cold, and in the first mile or so of travel, it will sometimes stutter a bit (almost feels like a learner driver with the kangaroo style of driving). When this happens, if I get to car to over 3000rpm, it might be ok (stutters in maybe 2nd and 3rd gears), otherwise I will suffer the limp home. A quick cycle of the ignition to clear it. If I am unlucky then it might happen as I pull away from the next roundabout (all within a mile or so of work). Generally after that the car is ok, unless I ask it for some power - like a fast overtake up a hill after 60+ minutes of driving. It pulls ok up to about 3000rpm and then limp home mode kicks on, and it is game over. If I am lucky I have enough speed to get past the vehicle and pull in safely, and make it to the top of the hill before I can cycle the ignition to clear the fault.

The chances are this is caused by a sticky/dirty VNT mechanism in the turbo. I am planning on taking my turbo off when the weather is a fraction nicer and attempting to clean it up. If I don't fancy taking it apart, then there are companies which will clean it up for you (from £150), and some freedom members on here offer such a service too (cost unknown)

If the oil line was clogged, then I think in all honesty then the turbo would be well and truly and knackered and it would not work at all! If you can find someone local to you with vag-com (or you have a friendly dealer) then get the fault code checks - I suspect you will see "Overboost" logged, clear the code, and then next time limp-home occurs that fault will be back.

It might be worth just checking the n75 valve (picture - n75 & MAF) and associated pipework is clear. you can pull the pipe from the n75 which goes to the turbo off, and suck it. If you have slim enough arms you can reach down to the turbo (do this when the engine is cold) and you should feel a smooth movement, if it is sticky (like mine is), then that is probably the problem.

Skoda dealers won't fix this, they will just sell you a whole new turbo, at a cost of about £600 + 3 hours labour.

CTS, MAF and n75 can all cause turbo issues as well, CTS is cheap and easy to replace, best bet is to get a vag-com scan done and see if there any reported faults. The CTS has two feeds - one for the dash guage, and one for the ECU, so only part of might be faulty.....

hth

Edited 13 April, 2010 by mbames

[pandj]

Hi, and thanks for a quick and helpful reply. I will get a diagnostic done and go for replacing the CTS - looking at Euro-Carparts they are cheap enough, but there are two units shown, but the VIN number should sort that.

I should also mention that I'm now trying a different technique of first start-up having read some advise on diesel turbo's elsewhere. I let the engine idle for 30 - secs 60, before driving away and then idle again before switching off. I don't know how beneficial this really is to the turbo, but until I learn otherwise..... It does seem to help, when I remember to do it, and also initally I am trying the quick short up through the gears technique so keeping the initial power revs down when the engine is cold. That does seem to work, but doesn't overcome the unpredicatable later entry into the "limp home" mode, which is not so easy for my wife when she is driving. No comments please about women drivers!

[Nick H]

How many miles has the car covered?

[KenONeill]

The turbo oil feed and return pretty much must be ok, because the turbo needs oil even more than the engine bearings do.

Losing power if you rev over 3_000 and an overboost engine code strongly suggest that the VVT nozzle vanes are gummed up.

There's no harm in letting the engine idle to get oil pressure up on a cold start, and cool the turbo if you've just come off a run turbo on, but if you've driven a mile or so at town speeds, with revs under 1_600 then the turbo will be as cool as it's going to get until you turn the engine off.

[pandj]

Hello,

Thank you for your replies.

The mileage is approx 65,000.

In order to clean the vanes, is there a sensible access route to the turbo, and does the it have to be withdrawn or can the work be done insitu?

Regarding the unsteady temperature readings, the thermostat was diagnosed as faulty, but just keeping an eye on the gauge to ensure all is now steady from the sensor. Again, thanks for the guidance.

[mbames]

The mileage is approx 65,000.

In order to clean the vanes, is there a sensible access route to the turbo, and does the it have to be withdrawn or can the work be done insitu?

turbo needs to come off for the VNT part of it to be cleaned up. When replacing it will need some replacement gaskets, and possibly a new oil feeder pipe (as sometimes these break when disconnecting the turbo).

[moley]

From your description I would think your problem is the sticking vanes on the turbo as it's a fairly common problem.

This link might help.

http://www.technologie-entwicklung.de/Gasturbines/VNT15-Turbo/vnt15-turbo.html

[cmcm789]

My car (2001 TDi110) does some very similar things. When cold, and in the first mile or so of travel, it will sometimes stutter a bit (almost feels like a learner driver with the kangaroo style of driving). When this happens, if I get to car to over 3000rpm, it might be ok (stutters in maybe 2nd and 3rd gears), otherwise I will suffer the limp home. A quick cycle of the ignition to clear it. If I am unlucky then it might happen as I pull away from the next roundabout (all within a mile or so of work). Generally after that the car is ok, unless I ask it for some power - like a fast overtake up a hill after 60+ minutes of driving. It pulls ok up to about 3000rpm and then limp home mode kicks on, and it is game over. If I am lucky I have enough speed to get past the vehicle and pull in safely, and make it to the top of the hill before I can cycle the ignition to clear the fault.

The chances are this is caused by a sticky/dirty VNT mechanism in the turbo. I am planning on taking my turbo off when the weather is a fraction nicer and attempting to clean it up. If I don't fancy taking it apart, then there are companies which will clean it up for you (from £150), and some freedom members on here offer such a service too (cost unknown)

If the oil line was clogged, then I think in all honesty then the turbo would be well and truly and knackered and it would not work at all! If you can find someone local to you with vag-com (or you have a friendly dealer) then get the fault code checks - I suspect you will see "Overboost" logged, clear the code, and then next time limp-home occurs that fault will be back.

It might be worth just checking the n75 valve (picture - n75 & MAF) and associated pipework is clear. you can pull the pipe from the n75 which goes to the turbo off, and suck it. If you have slim enough arms you can reach down to the turbo (do this when the engine is cold) and you should feel a smooth movement, if it is sticky (like mine is), then that is probably the problem.

Skoda dealers won't fix this, they will just sell you a whole new turbo, at a cost of about £600 + 3 hours labour.

CTS, MAF and n75 can all cause turbo issues as well, CTS is cheap and easy to replace, bet bet is to get a vag-com scan done and see if there any reported faults. The CTS has two feeds - one for the dash guage, and one for the ECU, so only fault of might be faulty.....

hth

I have exactly the same problem. 2003 110 TDI with 90k on the clock.

I can only dscribe it as running lumpy between 1,500 and 3,000 rpm when cold with a tendency to enter limp mode when revved beyond 3,000 rpm (sometimes at 4,000) even when the increase in acceleration is at snails pace.

Would be good i suppose to clean the turbo as suggested, but how difficult is this for a novice??

[mbames]

I have exactly the same problem. 2003 110 TDI with 90k on the clock.

I can only dscribe it as running lumpy between 1,500 and 3,000 rpm when cold with a tendency to enter limp mode when revved beyond 3,000 rpm (sometimes at 4,000) even when the increase in acceleration is at snails pace.

Would be good i suppose to clean the turbo as suggested, but how difficult is this for a novice??

I haven't taken the turbo off mine yet. last time I paid a local bloke to do it for me. He swapped my turbos over in a little under 3 hours, which was near enough what the local Skoda Dealer quoted me - 3 hours. I think that access to it is a little tight, as there is a driveshaft which can actually make getting the whole unit out rather difficult.

I have found that (if when cold) you pull off the lower left-hand pipe pipe from the n75 (this goes to the turbo), and suck on it, you should be able to apply a vacuum to the control arm on the turbo, and feel the external drive for the VNT working. I found that when I released the vacuum, it did not return to rest properly, and that if I actually blew down the pipe it suddenly "popped" back into place. I tried this a few times, but I think mine is very close to needing sorting! However I am in the middle of pulling down ceilings and about to put a new skylight in and rebuild a chimney, so lacking in time to play with the car at the moment.

I have also found when warm (say an hour into the drive), if you have to queue in traffic for say 10-15 mins, and then you pull away normally (not booting it), then it is pretty likely to go into "limp-home" mode too. I say that with quotes as sometimes it is most definitely a proper limp home, and other times, performance is cr@p but not as slow as limp mode.

[cmcm789]

As a follow up, for the last few weeks i have had no obvious issues with my car running poorly. Now sure exactly why, but it may be one of the following:

• Refuelling more from BP etc as opposed to supermarkets.
  
• Double dosage of millers diesel plus sport stuff (not sure of exact name). I have this in my car and add it to a tank of diesel about once every month or two, and usually when i get supermarket diesel. and finally,
  
• Putting the turbo/engine under pressure at very low revs in very high gears. I read this somewhere before that doing this move or opens up the turbo vanes fully (or something like this). I usually find a long hill near my home where i get my car to about 30mph (just over 1,000rpm) in 4th gear and accelerate full. Then when it reaches about 1,300rpm (takes a while as the hill is very steep and very long), i change into 5th and put my foot down again. I let the speed build up to about 50mph and then drive as normal.
  

Also, i still give it the odd blast every now and again.

It is possible that it's a combination of these, but whatever it is, the car is running fine for now and seems to be producing decent mpgs.

[KenONeill]

Not sure how effective cleaners will be, since the VVT is on the exhaust side, so the cleaner's been through the combustion chamber before it reaches the VVT. I'd suspect that exercising the VVT has more of an effect.

[lumac999]

CTS, MAF and n75 can all cause turbo issues as well, CTS is cheap and easy to replace, best bet is to get a vag-com scan done and see if there any reported faults. The CTS has two feeds - one for the dash guage, and one for the ECU, so only part of might be faulty.....

hth

What's the CTS?

Thanks

[mbames]

CTS = Coolant Temperature Sensor