1 hour ago, Breezy_Pete said:

 @PetrolDave what do you think about the lack of residual servo vacuum, please?  (On second thoughts, perhaps you don't drive diesels, going by the username. 😆)

I did have one diesel B6 A4 (a 1.9TDi Sport GmbH Avant) - I remember there always being some residual vacuum that took several presses of the brake pedal to 'use up'.

 

Sounds most like a vacuum leak or faulty non-return valve to me - but you've checked those, and if the brake pedal does gain assistance when the engine is running I *think* that rules out a faulty vacuum pump or servo diaphragm (but I could be wrong).

 

BTW I did once manage an average of 75mpg on a tank of normal diesel, but I was driving 'like a granny' 😂

Edited 2 December, 20241 yr by PetrolDave

On closer scrutiny,  there's a non-return valve right at the servo, in the bit at the end of the vacuum pipe that plugs in through a grommet. Will have to wrestle that out and test it.

5 hours ago, Breezy_Pete said:

There was zero residual servo vacuum. Double-checked that just now, that can't be right, right?

 

I find that most modern cars are like that especially those with electric vacuum pumps, when you think about it there are so many other vacuum actuators and leaky pipes. I only get one press on the pedal with very little assistance before having to man up!

 

I was towed in mine yesterday and had to use the brakes and steering without assistance, the former braking both vehicles to keep the rope taut (we are supposed to use a solid towbar here), it was OK, brakes a little better than I expected, the electric power steering was as heavy as expected but loads up even more if you turn it at anything more than very slowly, I prefer a hydraulic system unassisted as it feels like normal steering but with big sticky tyres.

7 hours ago, Graham Butcher said:

Oh yes, my bad, I forgot your car is a 57 plate, they started switching over to electric in 2012/13.

 

Your gut was sort of right, many VAG models started with electro-mechanical steering racks as far back as 2004, some models had electro-hydraulic as well, as in the Fabia/polo

No progress on the servo NRV; access is horrible in the scuttle, wiring conduit and A/C pipes in the way. Vaguely wondering about plumbing in a new, additional NRV somewhere more accessible.

Genuine replacement pipe is NLA, doubt there's anything aftermarket. 8E2 611 931M, dropped from supply by Audi a few months back. 

 

I replaced the foglight damaged by the deer crash today, as well as the ARB bushes and links.

The latter was suggested by a near neighbour as a possible solution to the clatter/knock I get at low speed on rough road surfaces. I will be pleasantly surprised if it's made any difference.  Couldn't see much wrong with what came off.

Oh, and of course, of the 8 ARB fasteners I had to undo, one seized and had to be sawn off. The joy of old cars.

 

 

Spoke to a helpful fella at my local TPS about the servo hose. Not able to order it any more and none showing at any TPS or dealership in the whole UK.  ☹️

 

Just messaged an ebay seller with a suitable vehicle listed as breaking.

 

Reluctant to do battle with it until I've got something that could fit in there if I destroy it trying to extract it, cos that would render the vehicle undrivable.

Our indy is breaking an A4 and may be able to help.  I'll PM you his phone number.

 

Thanks mainly to @Golf-Fiend and @SuperbTWM in another thread that has become a bit polluted; I've just grabbed some data that appears to show an issue with the timing, not sure how bad, but probably worth tweaking. 

Injector deviations also logged briefly, at or near idle, with warmish but <50°C engine.

I'm not sure what engine temps are best for logging either torsion value or deviations.

Anyone know if that -1.5 needs a clockwise or anticlockwise turn of the cam to reduce towards zero, please? 

 

 

Edited 15 December, 20241 yr by Breezy_Pete

The log has a couple of minutes more data, including a few blips of the throttle, which as per a youtube video I watched first, briefly reduces the torsion value to -1.0 each blip. Not much else seemed to vary.

 

 

Late to the party but I absolutely miss my pd130 octavia. Wishing you many years of happy motoring. Also.. post remap (more linear power delivery) made it a joy to drive.

I think moving the cam further towards the direction of rotation (clockwise) will yield a more positive result. I think the 3 bolts are 13mm and the centre bolt is something like 18 or 19mm

At least you have a baseline adjustment, I would put it to 0 or 0.5 and see how the car reacts to it over a week or so and also see what it does to the fuel economy.  
 

The injector values look quite good to me. I was seeing a bigger spread than that. Probably in the region of +1.0/1.5 to -1.0/1.5

 

Edited 15 December, 20241 yr by SuperbTWM

Ta. 

Think I might need to do some basics over the Christmas break, like checking that the belt isn't a whole tooth out, having a look at the cam and the injector loom.  Partner stalled it twice this morning without doing anything silly, so there's definitely something significantly amiss.

I'd better grab a gasket for the cam cover. 

 

Thanks for the support. 

Just done a quick google to refresh myself and thought it might be worth sharing this. It seems there may be some trial and error required in some cases and not a clear cut adjustment as I first thought 

Since first working on the PD motors, we found the setting of the torsion value a bit of a mystery. The torsion value is located in VCDS/Engine Module/ block 4/ torsion value. We tended to figure that 0.0 was a good figure and originally let it go at that.

However, early on, we had a Passat Wagon that lost 4 mpg when we set the torsion value to 0.0. The customer had us return the value to it's original setting of -.5 and the mileage came right back.

Now we find that the value can be positive or negative a much greater degree. Most recently, we checked the value on a car that was in for an oil change. The torsion value was set at -5.7 and the owner says her manual transmission car averages 45mpg and on a trip will get over 52mpg!

This is what we think is happening:

The only way to set the engine for TDC is by using a crank lock, such as that sold by Metalnerd. We have been providing their timing tools for several years. However well the tools are made, we find that the hole in the flange that is used to pin the crank sprocket into position has a movement of about 1-2 degrees. There is also a question about the accuracy of the location of the front flange location hole that the crank lock uses. I think the hole location in the flange could allow another 1-2 degrees of error.

The total deviation, given these two variables, could allow the crank setting to be off as much as 4 degrees, +/-. Since the cam position is relative to the crank timing, that can create a wide variation for each engine's correct torsion value. That would account for the reason one engine works well with a +2.5 reading, while another is working very well with a reading that is nearly -6.0.

There is no TDC mark on the flywheel,nor is there any other positioning reference besides the crank lock to locate TDC. That takes away any scientific method of relating the crank position to the cam position. 

The only way I know to accurately locate the true TDC mark is to remove the #1 injector and with a dial indicator and find the piston rolling through TDC. I have noticed that in the Passat, there is a hole that is on the side of the block where a mark could be made. This may also be true of the other PD motors. I will look. 

But unless there is a method by which you can determine accurately where the TDC actually is, the setting of the cam's torsion value will be experimentation.

Those wanting to optimize their fuel ecomony/ power should move the cam sprocket in relation to the cam shaft. Moving the cam shaft in the direction of rotation moves the cam torsion value in the positive direction. Just like the injection pumps for the ALH engine, the setting is very precise and a small adjustment makes a lot of difference. Movements of a few points and then either taking performance runs or recording mileage should give you an idea if there can be an improvement over the existing torsion value setting.

 

Interesting. Sounds like attempting to tweak that towards 0.0 just now might be a waste of time, unless I've got time and inclination to do a load of experimenting. Thanks again.

Potentially, I do apologise for getting your hopes up. Although given how easy it is to adjust, it wouldn’t take much to put it back. 

Another log this morning, on arrival after 35 minute drive to work has me wondering if the measured torsion value might be maxing out at -1.5. (VCDS says -3 to +3 when you hover over the box, but...)

 

Engine doesn't warm up properly to 90 due I think to thermostat not closing fully (new, genuine replacement a few months back), but the behaviour when mostly warm differs in that a throttle blip now doesn't reduce the negativity by 0.5.  Torsion number just sits solid on -1.5.

 

Or could it be that the disappointing economy is just related to the engine temperature not getting above about 80°C at the moment; I wonder?  Planning to revisit thermostat over the holiday.

 

 

 

 

LOG-01-004-012-013.xlsx

Edited 16 December, 20241 yr by Breezy_Pete
thought about temps

2 hours ago, Breezy_Pete said:

has me wondering if the measured torsion value might be maxing out at -1.5. (VCDS says -3 to +3 when you hover over the box, but...)

 

I think you are right Pete, on another thread I thought it was something small like 2° from memory on my BKD engine, 1.5° does ring a bell, but then on mine if it went beyond the 1.5° it would show a false zero, perhaps they have rewritten the code for it to remain stuck at 1.5°? I can see the logic in that.

 

Given how the engine is running, your partner stalling it etc you should go with your instinct and check the cam belt timing first, I bet you find its a 50/50 situation whether to move it one tooth or leave it where it is.

17 hours ago, SuperbTWM said:

However well the tools are made, we find that the hole in the flange that is used to pin the crank sprocket into position has a movement of about 1-2 degrees. There is also a question about the accuracy of the location of the front flange location hole that the crank lock uses. I think the hole location in the flange could allow another 1-2 degrees of error.

The total deviation, given these two variables, could allow the crank setting to be off as much as 4 degrees, +/-.

 

Not sure about that, isn't the crankshaft timing belt pulley and crank sensor trigger wheel keyed to the crankshaft?

 

I believe that aside from a loose or failing crankshaft sensor the engine management will recieve extremely accurate crankshaft position data, ditto for the cam position sensor.

 

The issue I believe they are referring to is when you lock the crankshaft at TDC it may be slightly out due to the clearance required for the locking pin, it will not be 1-2 degrees, that is complete nonsense even with an H7 clearance at that radius we are talking less than 0.2° angular error, say 0.5° if the crank has been moved and pinched the locking pin.

Edited 16 December, 20241 yr by J.R.

1 hour ago, J.R. said:

 

Not sure about that, isn't the crankshaft timing belt pulley and crank sensor trigger wheel keyed to the crankshaft?

 

I believe that aside from a loose or failing crankshaft sensor the engine management will recieve extremely accurate crankshaft position data, ditto for the cam position sensor.

 

The issue I believe they are referring to is when you lock the crankshaft at TDC it may be slightly out due to the clearance required for the locking pin, it will not be 1-2 degrees, that is complete nonsense even with an H7 clearance at that radius we are talking less than 0.2° angular error, say 0.5° if the crank has been moved and pinched the locking pin.

I’m not sure either. 
 

I think what they are trying to say is that the torsion value comes from the cam sensor only maybe? and not referenced to the crank/TDC therefore if the crank is off slightly the assumed TDC from the cam will be off giving you various readings of torsion that don’t quite mean anything. 
 

this is the only scenario I can make sense of it. As you say, if it was using both the crank and cam sensors together then it can’t be anything but spot on

 

I agree with checking the base timing first, then go from there

No, any measurement has to come from another datum, the camshaft position sensor values are referenced to the crankshaft position sensor.

 

An analogy would be trying to tell the time using a watch (analogue) that has no face and is perfectly round with no winder, no way of knowing where the 12.00 datum is.

 

The watch would keep perfect time but be useless.

On 16/12/2024 at 09:28, Breezy_Pete said:

Or could it be that the disappointing economy is just related to the engine temperature not getting above about 80°C at the moment; I wonder?  Planning to revisit thermostat over the holiday.

 

Is that rural steadyish driving and for how long? Those engines were notoriously slow to warm up and cool running, Doesn't the thermostat start to open at something like 86 degrees anyway? WIth the oil temperature taking considerably longer to warm up as well I doubt it would get to 90 unless you were on the motorway from what I can remember, especially for the current time of year

Yes, most of the roads round here don't ever get quiet enough to do anything other than modest speeds, but it just never gets to 90C within the first 12-15 miles of a journey, and usually seems to linger nearer 80.

Surprisingly, the dash gauge does seem to pretty accurately display what VCDS reads from both NTCs within the green dual sender. Oil temp is consistent with both of those two,  although I guess all three could be suffering downward drift. Might swap in a spare sender I've bought to see if it's all just an illusion.

 

 

Edited 17 December, 20241 yr by Breezy_Pete

Observed something interesting yesterday evening while looking at measuring blocks. Nothing I actually saw being weird in the measurements,  but with a mid-temperature engine idling in a car park, I found that I could make it feel like it was misfiring by raising the revs to a particular speed around 1150 or so. Whole car shaking a bit. Scanned through lots of MVBs while it was doing this without noticing any 'stand out' numbers anywhere! 

Going back to the injectors. The following seems to suggest injector deviation is only an issue if its larger than +/- 0.5 although it looks like another DIY article rather than concrete evidence.

 

https://www.myturbodiesel.com/d2/1000q/multi/PD-adjust-Idle-TDI.htm

 

 

5 minutes ago, Breezy_Pete said:

Observed something interesting yesterday evening while looking at measuring blocks. Nothing I actually saw being weird in the measurements,  but with a mid-temperature engine idling in a car park, I found that I could make it feel like it was misfiring by raising the revs to a particular speed around 1150 or so. Whole car shaking a bit. Scanned through lots of MVBs while it was doing this without noticing any 'stand out' numbers anywhere! 

 

Might just be the DMF? If I raise the idle slightly in my Passat to just over 1000 and hold it there I get the same increased wobblyness that can be felt while in the drivers seat. Smooth as silk in the rest of the rev range

Edited 17 December, 20241 yr by SuperbTWM