OT: Paging VAGisti

Anyone got any experience of bother with the VAG 3cyl 1.4 TDI with ~75bhp?
Father has one fitted to his A2. Sometimes under load (going up a big
motorway hill for instance), it appears to stop producing boost. It's quite all-or-nothing in the power delivery stakes when its working properly and its a bit worrying to drive when it's unhappy.
After stopping and starting the engine it seems to clear and could be fine for the rest of the journey. No pretty lights appear on the dash to warn of anything untoward. It doesn't produce lots of black smoke. I think, but I could be wrong that it sounds a little bit different at idle when it's not running right.
Has anyone any suggestions of where to start looking for problems?
--
Douglas

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've had 2, worked fine.

Try to find someone with vag-com and do a run with logging. It sounds a bit like a couple of problems I have heard about with 1.9s first is that it's overboosting and the ECU panics though that's normally down to an over enthusiastic remap. As you don't say it has one and unless it started right after the remap then it's probably the N75 valve (unless the 1.4 has a different designation, it's the boost control solenoid) these can become stuck and again the ECU| shuts down into limp home mode. I'd start with the latter.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Has anyone any suggestions of where to start looking for problems?

That would be me - fully licenced copy on the other laptop and the lead.
However, you would need to check the interface. Not the physical one, but the system behind it.
My lead is not CAN bus, but the earlier system.
I will go and do a google on the A2, watch this space.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob Sherunckle wrote:

Mister Sherunckle. I was hoping you would respond...
Father's A2 is 2000 on a Y if that makes any difference.
If your copy of vag-com can help find out whats wrong that would be pretty cool.
--
Douglas

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's not 2000 if it's a Y plater. Y was 1st March til end of August 2001.
Peter
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Still ok it seems.
From what I can gather they all used K lne until 03 then CAN bus after that. (Apart from pre 95 stuff which uses a 2 + 2 pin interface.)
Right, what we need to do next is find the diagnostics port.
On the golf it is right in the dashboard behind a hidden panel accessed by removing the ashtray and sliding the panel sideways. (Very scooby doo mystery if you know what I mean).
Anyway - over to you SD.
I patiently await your detective work.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Try by the bonnet release. Other than that on the 6n polo it's by the fuse box. Be glad it's not the 2+2 as they tended not to be in a fixed place so much as a loose terminal behind the glovebox.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ok. it's in the knee panel in the drivers footwell next to the bonnet release.
Alegedly.
I'm sitting here with a fecked back right now.
How's about later in the afternoon when nothing much usefull is happening anyway - around about the long dark teatime of the soul or thereabouts.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob Sherunckle wrote:

Taking this to email.
--
Douglas

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob Sherunckle wrote of Audi A2 1.4 TDI :

You're quite correct.
Well probably. There's a big purple multiplug next to the bonnet release under a fusebox that looks like it might be used to talk computer.
--
Douglas

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That's it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
AstraVanMan wrote:

By Jupiter he's correct!
--
Douglas

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Depresion wrote:

Yeah this one's been pretty good really, it's done 100k over the last 5 or 6 years and this is the first bother there's been.

That was my first thought. The problem started after it was sitting unused for about 10 weeks this summer. It got an occasional run to the swimming pool and back, but that doesn't seem to have helped.
There's no remap - it's completely standard as far as I know.
I might see if I can take up Bob Sherunckle's kind offer of a shot at vag-com.
--
Douglas

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Douglas Payne wrote:

Yep, and it rocks.

Sticky N75 if you're lucky, sticky VNT turbo vanes if you're not.
http://forums.tdiclub.com/showthread.php?s ;7ef9e610b2dabf800709db7f65642d&t0910
Both will cause the symptons you're seeing: The turbo goes into overboost, and gets shut down by the ECU- cycling the power clears it. If the other poster with VAG-COM can get it connected, you'll probably see 'overboost detected' or similar.
The non-CAN VAG-COM will be fine on that model of Polo.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

What model's that? The Audi A2 model of Polo? :P
Peter
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
AstraVanMan wrote:

Arse. Not paying attention. My mind was on the Polo we had with that engine :-/
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Chris Bartram wrote:

Heh, it's very torquey. It's good for some things.

http://forums.tdiclub.com/showthread.php?s ;7ef9e610b2dabf800709db7f65642d&t0910

It's an Audi A2 (c;. But thanks for the links, you're a legend.
--
Douglas

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Douglas Payne wrote:

Arse. It'll be ok for the A2 as well :-). Like someone else said, anything up to 2003 is non-CAN. The MKII A3 was, I think, the earliest CAN-only car.
I was stuck with the thought of the Polo we had with that engine.
The links are probably more for the 1.9 engines, but the principle is the same. Hell, it might even be the same turbo. Whatever, the vanes stick due to soot and/or oil gunge, and it throws the ECU into limp home.
People will often shout 'MAF' at the first hint of power loss on a TDI, but MAF failure is usually just a general, all-the-time power loss. Your symptoms are classic boost control problems- which means the turbo/vnt actuator (the actuator isn't available seperately from VAG IIRC), the N75 control valve, or *maybe* a knackered hose. Sometimes you can free the actuator and vanes by working it manually, or by cycling it with an output test on VAG-COM. A search on TDIClub will reveal lots of info.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Chris Bartram wrote:

Bob Sherunckle has come up with the goods so to speak and interrogated the little Audi with VAG COM.
We didn't drive it because we can't be sure of replicating fault and its ferbluddyeezing here tonight.
The engine ECU had this fault code stored: 17964 Charge Pressure control negative deviation P1556-35-10 Intermittent.
Any ideas on what this actually means? Is it just more evidence for VNT/N75 issues? If it is either of these, are they easily DIY fixed or do you think it's time to have someone recon some stuff?
My father and I are relatively enthusiastic DIYers but it is his daily transport and if its easy for the inexperienced to make a mess of, I think I'd be more inclined to send it somewhere I know will make a decent job of it.
I'll have a root around on TDIClub in the meantime.
Thanks again.
--
Douglas

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I can't take credit for this:
17964/P1556 - Charge Pressure Control: Negative Deviation
Possible Causes Boost Pressure too Low Hoses/Pipes incorrect connected, disconnected or leaking Charger Pressure Control defective VNT (variable nozzle turbo): nozzles stuck Solenoid Valve for Boost Pressure Control (N75) defective
Possible Solutions Check Hoses/Pipes to/between Components Check Solenoid Valve for Boost Pressure Control (N75) Check / Clean / Replace Charge Pressure Control Check / Clean mechanism for variable nozzles
Retrieved from "http://wiki.ross-tech.com/index.php/17964/P1556/005462 "
Hope it's the N75 as it's a lot cheaper than a new turbo.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.