My van is experiencing disruptive Injector timing fluctuations, dramatically retarding injection timing for a moment.

So I am trying to track down the cause of this ‘coughing’ issue. The vehicle is our 2002 Caravelle with the 102 horsepower 2.5TDi AUF (because it was once an auto trans - essentially an ACV). Under acceleration it will momentarily die, jerking the vehicle.

On 4 June 2016 the day it started to ‘break down under acceleration, these codes found were …

17656 - Start of Injection Timing Regulation
P1248 - 35-10 - Control Deviation Intermittent

17977 - Cruise Control Switch
P1569 35-00 Implausible Signal

17654 - Needle Lift Sensor (G80)
P1246 - 35-10 - Implausible Signal Intermittent

Over the past couple of weeks this G80 code seems to be the one constant.

On 21 June i retrieved a couple of other codes …

17654 Manifold Pressure Sensor (G71)
P1156 - 35-00 - Open/Short to ground

17569 Manifold temperature Sensor (G72)
P1161 - 35-00 - Open/Short to Plus

And the intermittent …

17654 - Needle Lift Sensor (G80)
P1246 - 35-10 - Implausible Signal Intermittent

Often the car will drive for 20 - 100km without an issue and then start behaving like a kangaroo. Codes then return.

There has also been occasions that the idea seems rough, and times where the engine seems to lack power for a second or two.

Confounding issues have been …

1/ A coincidental failure of coolant sensors (temperature gauge on instrument panel and VAGCOM are both now saying 90 - before ether gauge wasn’t even registering!)

2/ In the mid-April 2016 there was an instance where the engine started and idle perfectly but would not respond to depressing accelerator pedal. My wife was convinced that it was due to the fact that I had just washed the windscreen. Quick ‘Google’ … Suspected failure of a bonnet switch ?? Ruptured rubber cap - high pressure stream of water entered space between bonnet and RH guard. Disconnected bonnet switch and shorted with a paperclip. Car drove normally without an issue for the next six weeks. We were pretty convinced that we had this issue nailed. However with the emergence of the current symptoms of ‘misfiring’ I initially suspected some intermittent fault with the bonnet switch. Broke the thing trying to disconnect it to test hypothesis. Experimented with this circuit both open and closed. Continuity seems to make no difference, calling into question earlier conclusions!!!

Interventions …

Checked continuity of Needle Lift Sensor. No shorts anywhere and impedances were (Not sure if mine is Bosch or Stanadyne - how do you tel this?)


Checked and adjusted the TDi timing left it sitting on 55 with a duty cycle slightly over 80%. injector timing was consistently showing the same figures for ‘calculated’ and ‘actual’. So that looked good.

(I recall seeing that at idle with injector timing accurate that the N108 duty cycle should be as low as 10%. Any ideas on what is within specification?)

Then tonight, with VAGCOM connected I was able to observe and graph what was actually happening to the timing when it misfires or loses power. There is a dramatic and instant retardation of the injector timing in the order of 10 to 15 degrees. So I can see how under load with the timing propelled well into the power stroke their would be no ignition. Sometimes these misfires would be isolated and this evening a significant run of them. (While I graphed it I’m a Mac refugee and running a laptop with XP am not sure how to capture the graphic.)

Where do you think I should look next?

Somehow, I expect to find that there are a number of conductors in a loom somewhere that are exposed and grounding ??

Track back from the N108 on the pump via the harness to the ECU? Im assuming this means surgery exposing conductors within sheath if there is nothing glaring detected by visualising/feeling the outside of the conduit.

Or am I barking up the wrong tree?

Finally, persistent codes (which I don’t think are relevant) relate to …

A ‘Missing Message from TCU’ (18034 P1626) This has not caused any issues to date. I threw away the TCU along with the automatic transmission and a couple of years back. Manual gearbox now!!

And the passenger side airbag showing a resistance too high - intermittent.

Looking forward and confident of remedying this but have times when my confidence and stomach for it wanes. My wife wearied of it about two weeks ago.

Living in rural Queensland Australia we are 200km to the nearest specialist VW service centre.

Am also interested in replacing nozzles. Just to sure if aI can get them shipped from UK and who here might do a remap!

This forum has been a wealth of knowledge to me, and while I have ploughed over a lot of conversations I optimistic that someone out there will help me put my finger on this one!!