(another) Limp mode TDI

[EdBe]

Hi, I’m having intermittent turbo failure on a 2002 1.9TDI Octavia Elegance 110bhp.
I know this topic comes round again and again (and i have read the other posts) but hope this will generate some interest ...:)

I’ve just phoned a skoda dealer for a price and advice on error code downloads and they gave me the general impression that on the older Octavias the fault codes can be a bit generic and they would have to set to testing components, something that I would enjoy doing anyway. . . .

Symptoms

Engine going into limp mode, always on a long hill under load and mostly in 4th gear around 3,000rpm

Also, occasionally there is a noise like “a person with a cold taking a sharp intake of breath” 2 or 3 times in succession on acceleration up a hill, this causes engine to back off with each noise, does not coincide with engine going into limp mode though.

Action taken so far

·The VNT lever was very stiff and movement seemed limited, I have worked the lever with a dowel rod and a release lubricant and movement has returned, the stiffness seems to be of similar level to our other car (1.9 TDI Octavia Ambiente 90bhp).

·On revving the engine the VNT moves, I have also vacuum tested the long pipe to the turbo which is ok.

·Have swapped the N75 from our ambiente to the elegance car but the valves must be of a different spec as elegance power was very limited with the ambiente N75.

·The N75 valve on the ambiente seems to have a better sound to it, “toc” when I manually sucked the pipes, the elegance one sounded a bit weepy but don’t know if the valve is one way or just restricted flow. I think the ambiente valve let flow both ways, although heavily restricted one way…

·The EGR butterfly valve seems to move freely, and when switching the engine on and off the vacuum plunger moves ok, which moves the VNT up and down ok. (or is that the N75 doing the latter ?)

·Running the engine with the EGR pipe (the one from the top of the EGR to the valve on the bulkhead) disconnected and plugged made no difference, still limped

·I have also cleaned the MAF if that makes any difference.


Has anyone got any ideas for further testing ?

Where is the MAP sensor and can I do any kind of test ? – is this attached to the inlet manifold ?

Any suggestions gratefully received

Thanks

Ed.

[ini]

If your MAF, N75 and control tubes are ok, it could be the MAP sensor (located on or around the intercooler on your cars)

It is most likely to be the vnt mechanism sticking. It's virtually impossible to tell if it is sticking by moving the actuator arm (unless it is really bad).

Here is some useful test & measurement info regarding the Pierburg parts (N75 etc):

http://www.geocities.com/tech4tdi/

http://www.ms-motor-service.com/ximages/pg_si_0065_en_web.pdf

http://www.ms-motor-service.com/ximages/pg_si_0076_en_web.pdf

http://www.msi-motor-service.com/ximages/PG_SI_0017_EN_WEB.pdf

http://www.msi-motor-service.com/ximages/PG_SI_0039_EN_WEB.pdf

http://www.ms-motor-service.com/ximages/pg_si_0079_en_web.pdf

http://www.ms-motor-service.com/ximages/pg_si_0077_en_web.pdf

[EdBe]

Wow, thanks for those. . .

That'll keep me busy for a while.. . .

Particularly interested with the info on the EPW valve (MAP ?) complaints of an audible squarking...

could be the "intake of breath" noise i am hearing on mine. .

lets get testing !

[greg123]

Not if you disconnect the actuator from the arm, or disconnect the actuator from it's mounting so you can feel the actual smoothness and stops in the mechanism without the actuator springing getting in the way. Agreed that the spring is so strong you won't feel anything if working against it.

Also agreed it's likely to be the VNT vanes, it's pretty easy to isolate the actuator & pipes via applying vacuum and running a N75 output cycle in vag-com.

I have started doing the VNT vanes rebuild for £125 (if turbo is sent to me) as normally the turbo it's self is absolutely fine, it just needs stripping down, the mech stripping down, threads tapping out and rebuilding with some anti-sieze. I really think most of the peple paying several hundred for a new turbo are in most cases spending money they don't need.

Due to the prevalance of the VNT vanes issue, I have started looking at the operation once I know it's an overboost causing the limp home before I look at piping/n75 etc, as normally you find seized or sticking VNT and need to look no further.

Greg.




It is most likely to be the vnt mechanism sticking. It's virtually impossible to tell if it is sticking by moving the actuator arm (unless it is really bad).

[EdBe]

TDi engine update, it did turn out to be the VNT mechanism at fault and had to be removed and cleaned etc. .

a big thanks to Greg for his help. .

I can thoroughly recommend http://www.small-engine.co.uk/

cheers

Ed.