2002 - Tdi 130 - Turbo Pressure negative deviation

[richard_gomm]

Hi all,

I have a problem with a Passat that some of you helped with previously, however it still exists and the garage have no idea where to go next.

To recap on the problem. I have a 2002 Passat 1.9 TDi 130 bhp, AWX engine code.

Intermitely (4 times in the past 4000 miles) the car loses a large amount of power, mainly struggling in 3 or 4 th gear. With the gas fully down in second theres no acclration until around 4000 revs. Then its only a little boost.

Diagnostics so far:
Previously I have been able to resolve the issue by turning the engine off. Openning the fuel cap to allow air into the tnk and starting the engine. However it hasn't work this time.

The car has gone into the garage and they found a fault code:

17964 - Charge Pressure - Negative deviation in Turbocharger wastgate regulator valve.

The garage removed the hose leading into the regulator. They said it had a leak on the hose and replaced it. They also checked the voltage and impedance on the unit it connected into - they read 12.34 volts and 16 ohm so in range for the device. Next they deleted the code and tried the car out - still no acceleration.

The garage are now confused and not sure what to do next. Its been to two garages, one wanted to do a compression test as they felt it was misfiring. THe car does judder and jump when stationary indicating a missfire. However the second garage believe the misfire is due to this negative pressure.

On a side line when starting the car from cold a large amount of white smoke, smelling strongly of diesel (not oil) comes form the exhaust. Its enough to cloud the view in the rear mirror. It only happens on first startup from cold.

Any thoughts anyone? I've seen that some people on here have the same problem and are talking about a N75 - is that the unit I mentioned above??
thanks for all your help.
Richard

[Mike McKinstry]

Have you had any other fault codes apart from the one mentioned? A misfire could be injector wiring loom breaking down which can be intermittent but usually shows itself as misfire injector -this can also be reset with ignition sometimes-however this is a very different sensation to going into limp mode .I have experienced both 1st hand!
Negative dev . is not overboost so i would have thought a leaky hose could have been a good bet .Some of the more knowledgable guys on here may be able to help more as alot of the limp mode faults discussed already only relate to 17965 not "64". If it is neg dev.could that be turbo sticking at closed position-unlikely if in 3rd/4th or again faulty N75 not supplying vacuum-

experts?

[richard_gomm]

Hi - thanks for the reply.

At the moment I'm not sure if it is limp mode or not. The garage wiped the code from the system - turned the engine off and back on. The code didn't appear. However the car still lacks power.

I would have thougt that if it went back into limp mode the error code would re-appear straight away?? It does come back but only after a few more enigne off / on's.

Theres been no other codes (except an abs brake switch which will be resolved next week with a new switch)

Since the pipes have been replaced - I think I'll be looking at a new N75 first and see what happens. Although there has been mention of a stuck rod actuator - I'm just working out how to check that!

thanks again

Richard

[richard_gomm]

sorry - rod acutator was meant to read Vane Adjusting Rod

[richard_gomm]

After a day out on the car I've come up with something new - not sure if it means anything to anyone, but thought I'd post it.

I've disconnected the MAF and took the car for a spin, it still has no power. The turbo doesn't seem to kick in till around 3000 revs (used to be a lot lower)

As a test I pulled off the vacum hose that goes into the vnt - I was expecting a hiss or sound of air escaping but I heard nothing... is that normal?

I reconnected it and blew into one of the tube (very hard, almost passed out ;-) and I hear a hiss of air coming out of somewhere.

I'm guessing that I have a leak in the vacum somewhere which I assume would give the negative pressure error??

I also checked the vnt rod - it moves freely up and down with little effort from me.

thanks again for the help

[richard_gomm]

Have you had any other fault codes apart from the one mentioned? A misfire could be injector wiring loom breaking down which can be intermittent but usually shows itself as misfire injector -this can also be reset with ignition sometimes-however this is a very different sensation to going into limp mode .I have experienced both 1st hand!
Negative dev . is not overboost so i would have thought a leaky hose could have been a good bet .Some of the more knowledgable guys on here may be able to help more as alot of the limp mode faults discussed already only relate to 17965 not "64". If it is neg dev.could that be turbo sticking at closed position-unlikely if in 3rd/4th or again faulty N75 not supplying vacuum-

experts?

Hi all.

I finally got a cable and shareware copy of vag-com. I've hooked it this morning and taken a load of readings from groups 001 - 025 at both idle and 3000 revs. Got tons of results but not too sure which areas I should be looking at.

Also the car has developed another fault code since I played with it the other day. I'm pretty sure thats whats causing the exessive smoking.

The faults as reported now are:

17964 - p1556 - Charge Pressure Contr. Negative Deviation
17552 - p1144 - Mass or Volume Air Flow Circ Open/Short to Ground

I'm assuming the second one is causing the white smoke on accerlation?? not enough air getting into the mix so the car throws out the fuel vapor - or does it not affect it that way?

Lastly I saw the group that showed glow plugs, with engine off but igination on I had two of the digits showing 1 (off) and all the others as 0. After the engine started they all went to 1. Am I assuming that this means I have two plugs out?

If anyone is interested in the figures vag-com throw out I'll paste them, if you let me know which groups (001 - 025)

If you actualy wnat to see the smoke and sick engine noise:
www.youtube.com/watch?v=RBgCa__sQoc

thanks

Richard

[smokey0123]

The sencond code is from where you ran it with the MAF disconected, now youve got vag com I would do a live data road test on the MAF and boost pressure.

[richard_gomm]

hi - thainks. which groups would you suggest i look at whilst driving? any area of the test to read in particular? I've done them at idle and 3000 revs stationary.

thanks

richard

[smokey0123]

Have a look here http://www.ross-tech.com/vag-com/cars/tdi.html

[richard_gomm]

Have a look here http://www.ross-tech.com/vag-com/cars/tdi.html

thanks, I've just run those tests (although the car struggled to reach 3500 revs in 4th!)

For the air system part 1 MAF test (from that page)
Took the car out got it to 200 revs in 4th. Floored the gas and eventually reached 3300 revs (it didn't want to go any faster)



For the Air System part 1: Turbo test.
same circs as above.



mean anything to anyone??