2001 1.9Tdi Auto - jerky gear changes

[MattD]

Anyone got any ideas what may be causing a jerky gearchange in a 1.9tdi automatic?
It's my former car, now driven by my mum.  Done about 120k miles - been well maintained.

She says it's sticking at around 3500 rpm and not happy changing up  - and jerking when it does.

I had a feeling it might be going into limp mode - struggling up hills and perhaps turbo not kicking in.  Loss of power or something. 

I haven't driven it myself - got her to burn up and down a dual carriageway in case turbo vanes were getting a bit clogged.

I'd appreciate any suggestions of where to look.

[Mirez]

When was the autobox fluid last changed? As a first port of call I would look to change this as auto-boxes are somewhat critical on fluid quality and quantity.

[MattD]

Thanks for the suggestion.  I had the gearbox refurbished by a reputable automatic gearbox specialist about 6 or 7 years ago - can't remember the exact issue at the time - something about not engaging 4th gear properly.  I presume the fluid was new and correct then - it's probably done 50k miles since.   I'll get the fluid checked out and changed if necessary, but I was under the impression that it was all sealed and didn't need maintenance?

[insanitybeard]

It might not be specified in the service schedule but that doesn't mean the oil doesn't degrade over time or that the transmission doesn't benefit from having it renewed- my own personal take on it is my final reply in this thread.

The actual procedure itself is covered here.

[MattD]

I now have first hand experience of driving itt - I'm 99% convinced it's an engine issue, not the gearbox..
From the minute it starts (which it does instantly - no issue there) it sounds as if it is firing on 3 cylinders, or 'lumpy'.   The car shakes as well.

It struggles to pull away a bit, but will get up to 70 in the end but it's reluctant to change up a gear, and is a bit jerky when it does (same changing down).   Fuel consumption looks a bit pants as well.    Feels like it's very underpowered - no idea if the turbo is kicking in or not - suspect not.  The 'lumpy' feeling is continuous.

Any idea where to start?  Apparently there are no faults showing, but I suspect a more complete VCDS investigation might show something.

[insanitybeard]

If it was a manual I would have thought you might have been describing dual mass flywheel issues! So is it running rough all the time then? Sticking vanes in the variable geometry turbos can cause loss of power but that shouldn't cause rough running/ problems at idle, nor would split boost hoses. Dodgy contacts on the injector wiring loom usually register a fault, but from what I've read tend to be more intermittent than continuous.

In the absence of any fault codes to work with, if it's definitely an engine running issue I'd be looking at things like a dodgy MAF sensor, EGR valve stuck open, relay 109 playing up, valve timing if the timing belt is nearing the point where it's due for renewal (or if it has recently been renewed), or fuel system problems. It's not losing coolant is it?

[MattD]

I'm not aware of coolant loss.  It's definitely rough from start up and continuous, even when warm  - it revs to 3500 without shutting down, so it can't be a catastrphic failure anywhere or something would trip to limp mode.

The only thing which has changed recently is that I put a new battery on about 2 weeks back, which would have involved there being no power for a while - could the ECU have reset itself to some default setting, where it had previously been coping/compensating with a gradual failure somewhere?

I've ordered a VCDS cable and I will have a look at the things you suggest.   At least then I can see errors first hand if there are any.

I know the cam belt was done about a year ago, but I don't remember the MAF or EGR valve having been looked at let alone replaced in the 10 years we have owned it. 

Hey ho - just have to hope it keeps limping on until I can fix it - mum wants to abandon it any buy something new, but that feels like a waste if Ã,£150 and a few hours effort will fix it.

[Chrispb]

This certainly sounds like injector wiring loom but will be confirmed with VCDS.

[MattD]

Update:

VCDS showed the following:

18075 -  PD Unit Injector; Cylinder 2 (N241): Electrical Malfunction

        P1667 - 35-10 -   - - Intermittent

and the autobox was complaining about 'low engine torque' which I imagine is not unreasonable if 1/4 of the engine isn't doing much.

So I now strongly suspect that a wiring loom is the obvious next step - and not so expensive that its a massive step.   Is there a guide to getting at it anywhere on the forum?  Also - which cylinder is no2 when viewed from the front? - might as well have a look and see if it is an obvious connector issue.

[insanitybeard]

No guide to replacement of that loom in the reference library as yet I believe, bear in mind the rocker cover has to come off to access the injector loom connectors onto the injectors themselves, and you'll likely need to remove the battery and the trim that encloses the engine side of the battery compartment in order to slide it out of the cylinder head (or make a hole in said trim with a hole cutter!). There was some discussion on it here.

If you do the job you could always take some pictures and submit them so that a reference library article could be written! 

I would think the cylinders would be numbered starting from the timing belt end but don't 100% take my word on that!

[MattD]

I changed the injector loom and it now runs and changes gear very smoothly. Ã,£67 from the VW dealer well spent.
I cleared faults and did a short test drive -  no faults showing either on engine or auto gearbox afterwards - so happy days there.

The only problem is that I can't get the rear valve cover bolts tightened properly  I used a 1/4" drive socket on a UJ to get them off, which was a fiddle getting round what I think is the EGR valve, but eventually I did it.  But it doesn't seem to be working in reverse - not sure if there is an angle I'm not getting right.

I now need to take it to somebody with more patience than me to get it sorted. 

How did we ever fix things before the internet ?- I would never have got this far without being able to consult experts and forums.

Thanks to all for the suggestions.

[Mirez]

Good work, great fix!

How did we ever fix things before the internet ?- I would never have got this far without being able to consult experts and forums.

Yeah its great when everyone helps each other on here. BTW did you take photo's?

[Chrispb]