Transporter T6 (CXHA) tapping/ticking/clicking under acceleration

[T6uno]

Hi all,

I’ve been having some trouble with my T6 these past couple of weeks, it’s making a tapping/ticking/clicking noise under acceleration, it seems to be more prominent when hitting over 2k revs

It’s also hesitant to start, but does fire up after a few seconds, it sounds like the engine starts up twice if that makes sense (or in 2 halves)

I’ve looked under the hood and noticed potential leaking from one of the injectors (I suspect an injector is the issue), a week before all this happened I used some Wynn’s Xtreme Diesel System Clean with around 20 litres of diesel in the tank, I’m not sure if that was too neat and maybe caused some of my issues (Wynn states 20-30 litres)

I only ever run the van on shell premium fuel so not sure if the Diesel Clean was even needed

Hoping to do a leak off test on the injectors next weekend

I purchased VCDS from Gendan hoping for it to help me with issues such as this but I’m still learning how to use it, I dropped @mmi a private message and he’s offered to help me out with diagnosing it on the basis that it’s made public to help anyone in the future suffering with the same issue

Thanks

T6Uno

 

[mmi]

Let's start collecting a "base-line" data package

Please post the following

1) Full VCDS Auto-Scan
2) Engine blockmap - Ignition ON/engine OFF
3) Engine blockmap - Engine running at idle
4) Engine blockmap - Engine running at idle - 3 minutes after startup

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How-to create a VCDS Auto-Scan

Ignition ON

[VCDS]
[Auto-Scan]
Use default settings - Auto-detect (CAN only) - etc.
[Start]
Results [Save]

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How-to create a blockmap file:

[VCDS]
[Applications]
[Controller Channel Map]
- Single Controller Address = 01
- Login or security access code: Leave blank
- Function: Measuring values
- Output: CSV file
[Go]

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The result (TXT and CSV) files are saved into directory C:\Ross-Tech\VCDS\Logs
Please attach the files here.

 

[T6uno]

Here’s some images from around the injector site, as you can see something’s definitely leaking, about to hook up VCDS now so will dump some data shortly

 

[T6uno]

@mmi here are the logs as requested, if you need anything else just let me know

Thanks!

 

[mmi]

Any idea when the cam timing belt has been renewed? The camshaft phase position is quite far off - which quite possibly will eventually cause e.g. starting issues. The values below normally do not deviate much from zero (< ±2 °)



Time to renew the timing belt ??

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Post in thread 'Won’t start [Resolved]'

2 Aug 2021

I have downloaded the files you requested. I'm now going to remove battery and check fuses/relays etc as there was this burning smell that I presumed was the egr pipe but would be good if it's a melted relay.
Thanks to
mmi and Dellmassive

Thanks- indeed strange.
Have you scanned for the faults again after all the cranking? Directly under Engine - Fault Codes?
The last bits of data are under Engine - Advanced ID. Perhaps you could do that too?

Nothing obvious in the blockmap file - these two are interesting (and different to mine). Something "sporadic" was recorded starting...

• mmi

• 

 

[T6uno]

Any idea when the cam timing belt has been renewed? The camshaft phase position is quite far off - which quite possibly will eventually cause e.g. starting issues. The values below normally do not deviate much from zero (< ±2 °)

View attachment 316805

Time to renew the timing belt ??

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Post in thread 'Won’t start [Resolved]'

2 Aug 2021

I have downloaded the files you requested. I'm now going to remove battery and check fuses/relays etc as there was this burning smell that I presumed was the egr pipe but would be good if it's a melted relay.
Thanks to
mmi and Dellmassive

Thanks- indeed strange.
Have you scanned for the faults again after all the cranking? Directly under Engine - Fault Codes?
The last bits of data are under Engine - Advanced ID. Perhaps you could do that too?

Nothing obvious in the blockmap file - these two are interesting (and different to mine). Something "sporadic" was recorded starting...

• mmi

• 

Hi mate,

The timing belt was changed in April 2025 and had a full (major) service, all glowplugs were renewed at the same time, and the crankshaft pulley was found to be hanging on for dear life by 2 bolts so that was replaced also

All work was carried out by Steven at SB Motors (ex VW Mechanic, held in high regards amongst the community)

 

[T6uno]

I also wanted to add this image I took a few days ago when playing around with VCDS with the engine running and using some suggestions from previous posts on this forum

Am I right in thinking 248.7 Nm for Cylinder 3 bank 1 internal moment is pretty low, at the time it was even lower than that but then went up to 248.7 Nm

 

[mmi]

Hi mate,

The timing belt was changed in April 2025 and had a full (major) service, all glowplugs were renewed at the same time, and the crankshaft pulley was found to be hanging on for dear life by 2 bolts so that was replaced also

All work was carried out by Steven at SB Motors (ex VW Mechanic, held in high regards amongst the community)

Ok. But still the ECU sees a phase difference between crankshaft and camshaft (sensors) - possibly spun camshaft? --> Won’t start. No fault codes

Am I right in thinking 248.7 Nm for Cylinder 3 bank 1 internal moment is pretty low, at the time it was even lower than that but then went up to 248.7 Nm

Correct - the internal moments should be about the same for all cylinders.
Did you log the data?

 

[T6uno]

Just realised I also have the log for that attempt a few nights ago, not sure if it’s any help

 

[mmi]

Am I right in thinking 248.7 Nm for Cylinder 3 bank 1 internal moment is pretty low, at the time it was even lower than that but then went up to 248.7 Nm

Just realised I also have the log for that attempt a few nights ago, not sure if it’s any help

Well, the engine seems to run very poorly for the first 50 seconds, then just poorly. A bit mysterious wake-up at 53 seconds for cylinder 3. Perhaps record also IDE07742 Cylinder head: pressure sensor 3 bank 1: raw value (drop IDE00351 Main injection: start of activation)



The ECU tries to stabilise the run by adjusting injection duration.


Should be something like this (snippet from Lumpy engine start and idle )

(

 

[T6uno]

I dropped the fuel injection deviation time from the log and the main injection start of activation

Really weird as it seems the Cylinder 3 bank 1 internal moment is behaving much better today

I started logging with the engine switched off then started it and continued logging for around 4+ minutes

I’ve also attached a video of me starting the van (same time as I was logging) so you can hear it struggling to start, once the vans started if I switch it off and start it again it doesn’t struggle at all

Video Unavailable

This video is unavailable.

streamable.com

 

[T6uno]

Here’s a video of how the van behaves/starts after already being started

Watch unnamed | Streamable

Watch "unnamed" on Streamable.

streamable.com

 

[T6uno]

Ok so I just gave it a good boot down the motorway and the coil light came on, I pulled the code and it was
P0087 Fuel Rail/System Pressure - Too Low

 

[T6uno]

It’s reminding me a lot of this thread which turned out to be an injector….

https://www.t6forum.com/threads/vw-...jerks-and-judders-av-2-3k-rpm-problems.54253/

 

[mmi]

Really weird as it seems the Cylinder 3 bank 1 internal moment is behaving much better today

Yes, indeed. It's no different than the rest of them.

I’ve also attached a video of me starting the van (same time as I was logging) so you can hear it struggling to start

Seems it was struggling possibly because of quite low fuel pressure. See below - it took more than two seconds (4...6 sec) to build the nominal 300 bar. Normal would be about 0.5 seconds. Dashed green (at 4.0 sec) to note when ECU started to fire the injectors.

It’s reminding me a lot of this thread which turned out to be an injector….

Leaking injector is a possible cause for fuel pressure loss.

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For comparison a normal pressure build-up

 

[T6uno]

Update:

Changed the third injector today and initially things ended up even worse than before



Made sure I had coded it in right, checked all connections but the van was taking a while to start up when turning it over and when it did start the van was shaking and miss firing

At this point I felt defeated but decided to take the van on the motorway and give it a good run, and hey presto it sorted itself out



I’m thinking there might have been some air trapped in the system from replacing the injector that later cleared itself, but happy it’s all working now, the vans running like a dream!