204 DSG intermittent momentary power loss

[ben3042]

I'm not sure. I'll do similar runs with mine (same CXEB engine) to get more data. A 30 minute capture today didn't have any of the drop-outs with these - but I didn't push it that much.

IDE07785 Turbine actuator 1 bank 1: posit.feedback - Actual value​

IDE07793 Turboc.1 turbin.bypass valve 1 B. 1: pos.feedback - Actual value​

IDE08138 Bypass valve for turboch 2 turbine inlet: activation​

Morning MMI,
I've ordered a new VCDS Hex-V2 cable, should be here tomorrow. So I'll get a new log file once it's here, so that we can look at data with a decent logging rate.
Just thinking about the 3 channels dropping out, I'm trying to understand what could cause that. It's unlikely that all 3 solenoid valves would fail at the same time, so they must be being driven/controlled from another sensor? Something like the G31 sensor in the thread you linked earlier? I am not sure on the setup of these systems! But it sounds like from what you've seen, these 3 channels should not be dropping out like that under acceleration?

 

[mmi]

Ok - results from my engine - by doing presumably the same - hard acceleration with foot down (not engaging kick down). DSG at manual. From 1012 to 1020 seconds
Basically the same as yours with bypass valves - they do activate to limit the pressure. Also reaction of turbine actuator is similar.




It seems the better resolution will be useful. Below a copy from post#17.
Is it the dip in air mass (green) the concern - or actually the bump in turbine actuator (red)?



Interestingly there is quite a difference in maximum charge pressure

 

[ben3042]

Ok - results from my engine - by doing presumably the same - hard acceleration with foot down (not engaging kick down). DSG at manual. From 1012 to 1020 seconds
Basically the same as yours with bypass valves - they do activate to limit the pressure. Also reaction of turbine actuator is similar.


View attachment 210462

It seems the better resolution will be useful. Below a copy from post#17.
Is it the dip in air mass (green) the concern - or actually the bump in turbine actuator (red)?

View attachment 210463

Interestingly there is quite a difference in maximum charge pressure View attachment 210465

Very interesting stuff! Thankyou for the comparison data/graphs! Really useful to see the same data from a known good vehicle.
Yes I think the improved resolution should make things clearer. I’ll hopefully have a new data package and engine block data for you tomorrow evening!
Extra charge pressure could be the pendle map on my van? Is yours stock? Mine has been mapped for 3 years with no issue

 

[mmi]

Extra charge pressure could be the pendle map on my van? Is yours stock?

Yes, the only way squeeze more torque is to increase charge pressure thus ingesting more oxygen and fuel for higher output.
Mine is plain stock engine.

 

[mmi]

I've ordered a new VCDS Hex-V2 cable, should be here tomorrow.

By the way, the secret of the high data sampling rate is to tick the following


The main thing is the "Group UDS requests by 7" or 8 (these should work, the others not so well).
Ticking also bypass "Bypass Windows Timers" still improves the rate a bit.

 

[ben3042]

By the way, the secret of the high data sampling rate is to tick the following
View attachment 210487

The main thing is the "Group UDS requests by 7" or 8 (these should work, the others not so well).
Ticking also bypass "Bypass Windows Timers" still improves the a bit.

Great thanks for the tip! I’m looking forward to getting some decent data tomorrow evening and hopefully unearthing this gremlin!

 

[ben3042]

Hi MMI,
Last night turned in to a very busy evening! I managed to get a log with the new cable on the outward journey of trip out driving normally. The van didn't noticeably glitch, but that's not to say that it didn't do it, just that I didn't feel it (I realise the more torque being supplied, the more noticeable a sudden glitch!). I'll do another run this morning with harsh accels to try and force the glitch and also get you a blockmap file. Annoyingly, it glitched 5 or times on the return journey, but I didn't have the data logging set up!

 

[ben3042]

Hi MMI,
Blockmap attached. It took about 15 minutes to complete! is that normal?
I then did a data log on my way out to get fuel but it didnt glitch (short journey though). Before setting off home, I reset the EGR adaptions as I hadn't been able to do that with my old cable since changing the EGR.
Then took a longer drive home and managed to get it to glitch 7 times in the log file attached (with markers).
I really hope this shows something up!!!

 

[ben3042]

MMI, does the MAF signal in the last data set look right to you? It looks a bit noisy but it also dips out right at the point that the engine glitches (actually, slightly advanced from the dip in charge pressure, i.e. charge pressure dips as a result of the MAF dip). My thinking being, if the engine was glitching from something else, downstream of the air mass, I'd expect the air mass signal to dip AFTER the charge pressure dips as a result of the engine momentarily slowly down and sucking less air, but because it dips BEFORE, it could be the cause of the issue?

 

[ben3042]

Just popped the MAF sensor off to have a look…. does this look right to you? Looks dirty and odd that the blue coating has come away on the ‘bulge’

 

[mmi]

Blockmap attached. It took about 15 minutes to complete! is that normal?

Well, something obviously went wrong... and it's only half way. On screen you should see data channels running very fast.

Normally it takes about 65 seconds, and quite a few more lines in the data (see below):

 

[ben3042]

View attachment 210659
Well, something obviously went wrong... and it's only half way. On screen you should see data channels running very fast.

Normally it takes about 65 seconds, and quite a few more lines in the data (see below):
View attachment 210660

Yes it did run through very fast for the first half but then impossibly slow the second half. I’ll try again later!

 

[mmi]

Then took a longer drive home and managed to get it to glitch 7 times in the log file attached (with markers).
I really hope this shows something up!!!

Thank you very much. Indeed a lot to digest! I think now the glitch can be pinpointed very clearly - just remaining the chicken or egg situation. Anyways, here are the first appetisers - food for thought.

Markers in the file were at 500, 534, 540, 576, 578, 583, 613 seconds - so we hopefully can see something just before those.

(1) Around 613 second marker​

The speed (scaled here x18 just to get in the plot) just to give idea that there is significant acceleration.
In the injection duration the "flat" portion indicates that foot was off the throttle (as well as the torque in the picture below).

 

[mmi]

Hmmm... engine RPM reading jumps around really badly at the reported glitches. The engine definitely can't do 500 RPM jump in 0.1 seconds as below at 583 seconds. Could it be as simple as engine speed sensor, or crankcamshaft speed sensor??? One would expect to see nice smooth lines?
When the timing belt has been serviced?

 

[mmi]

 

[ben3042]

Hmmm... engine RPM reading jumps around really badly at the reported glitches. The engine definitely can't do 500 RPM jump in 0.1 seconds as below at 583 seconds. Could it be as simple as engine speed sensor, or crankcamshaft speed sensor??? One would expect to see nice smooth lines?
When the timing belt has been serviced?

View attachment 210695

View attachment 210696



View attachment 210699

Hi MMI,
Another great set of graphs and feedback! Thankyou!!
Hmm yes, the engine speed doesn't look as smooth as it should be. I changed the timing belt in April last year, 17,000 miles ago. I did have a spurious code a number of months ago for crankshaft or camshaft (cant remember now) sensor implausible signal. But after being cleared it never came back.
What are your thoughts on the MAF signal? and the picture of my MAF sensor? I've ordered a new one as mine definitely has some coating missing on the inlet sensor which is bound to affect something, even if not this.
Maybe it's worth buying a new crankshaft sensor and sticking it on for the sake of it? Is that where you'd put your money if you were a betting man do you think?

 

[mmi]

What are your thoughts on the MAF signal? and the picture of my MAF sensor? I've ordered a new one as mine definitely has some coating missing on the inlet sensor which is bound to affect something, even if not this.

It's quite difficult to comment the MAF signal - certainly it is affected by the glitches but I'd like to think it's the consequence. I have thought the error in air mass shouldn't have drastic sudden effect on engine power. Also EGR valve does very rapid movements which affect significantly to air flow.

Re the picture I don't remember seeing the blue stuff on mine (a few months ago) and mine was very clean. Anyways, not a bad investment to replace it as they won't last forever.

Maybe it's worth buying a new crankshaft sensor and sticking it on for the sake of it? Is that where you'd put your money if you were a betting man do you think?

Yes, I would put my money on engine speed sensor - especially now knowing about implausible signal (of ?) in the past.
Well, if you drive would be interesting to have a log with these parameters - to trace any delta between crankshaft and camshaft sensors. In the list there are several items related to engine RPM but not exactly sure if they are any different - if even the item named as Camshaft actually is camshaft.

IDE00021 Engine RPM​

IDE00075 Vehicle speed​

IDE00182 Camshaft adaptation intake bank 1: phase position​

IDE00347 Air mass: actual value​

IDE00352 Main injection: duration of activation​

IDE00405 Crankshaft speed (RPM)​

IDE00406 Camshaft RPM​

IDE04685 Setpoint generation interior torque​

IDE07742 Cylinder head: pressure sensor 3 bank 1: raw value​

ENG113719 ESM_Engine_speed​

ENG126001 P_L_Aps_crankshaft_speed​

ENG126043-ENG126092 P_L_Aps_camshaft_drift_angle-Camshaft target wheel drift angle​

​

I reset the EGR adaptions as I hadn't been able to do that with my old cable since changing the EGR.

This also relates to new capabilities with modern controllers of HEX-V2 cable

 

[ben3042]

It's quite difficult to comment the MAF signal - certainly it is affected by the glitches but I'd like to think it's the consequence. I have thought the error in air mass shouldn't have drastic sudden effect on engine power. Also EGR valve does very rapid movements which affect significantly to air flow.

Re the picture I don't remember seeing the blue stuff on mine (a few months ago) and mine was very clean. Anyways, not a bad investment to replace it as they won't last forever.



Yes, I would put my money on engine speed sensor - especially now knowing about implausible signal (of ?) in the past.
Well, if you drive would be interesting to have a log with these parameters - to trace any delta between crankshaft and camshaft sensors. In the list there are several items related to engine RPM but not exactly sure if they are any different - if even the item named as Camshaft actually is camshaft.

IDE00021 Engine RPM​

IDE00075 Vehicle speed​

IDE00182 Camshaft adaptation intake bank 1: phase position​

IDE00347 Air mass: actual value​

IDE00352 Main injection: duration of activation​

IDE00405 Crankshaft speed (RPM)​

IDE00406 Camshaft RPM​

IDE04685 Setpoint generation interior torque​

IDE07742 Cylinder head: pressure sensor 3 bank 1: raw value​

ENG113719 ESM_Engine_speed​

ENG126001 P_L_Aps_crankshaft_speed​

ENG126043-ENG126092 P_L_Aps_camshaft_drift_angle-Camshaft target wheel drift angle​

​

This also relates to new capabilities with modern controllers of HEX-V2 cable

Brilliant, thanks MMI I’ll get a log tomorrow morning of the new signals and see if that reveals anything. As you say, hopefully it shows one smooth signal and one noisy so the right sensor can be replaced!

 

[n10n]

Hmmm... engine RPM reading jumps around really badly at the reported glitches. The engine definitely can't do 500 RPM jump in 0.1 seconds as below at 583 seconds. Could it be as simple as engine speed sensor, or crankcamshaft speed sensor??? One would expect to see nice smooth lines?
When the timing belt has been serviced?

View attachment 210695

View attachment 210696



View attachment 210699

These look weird indeed. But they also look like moments of upshifting, especially the first one is very clear - the latter two I think are upshift followed by throttle pedal easing and engine braking.

So, could this be clutch playing up - slipping / slow to bite? 0.1s for 500rpm jump sounds fast but just thinking if throttle is basically floored when clutch opens it might be pretty quick.

 

[ben3042]

These look weird indeed. But they also look like moments of upshifting, especially the first one is very clear - the latter two I think are upshift followed by throttle pedal easing and engine braking.

So, could this be clutch playing up - slipping / slow to bite? 0.1s for 500rpm jump sounds fast but just thinking if throttle is basically floored when clutch opens it might be pretty quick.

I can see your thinking - when this first started happening, I initially suspected gearbox/clutch issues during upshift. But then realised it doesn’t actually happen during and upshift. It also happens during steady state.
And yes I see your point about change in engine speed but on these engines, 500rpm in 0.1s is not physically possible. If you floor it in neutral, the engine won’t spin up as quickly as that so it definitely cannot do it under partial/full load.
I’m going to log the engine speed sensors this morning and hopefully that will tell us something! Fingers crossed!!